The minimum Rust version is now 1.60.0 in order to use the dep: syntax for dependencies.

• switch cases with conditions that evaluate to constant () no longer optimize to false (should raise a type error during runtime).
• Fixes concatenation of BLOB's and strings, where the BLOB's should be interpreted as UTF-8 encoded strings.

• A new feature flag, no_custom_syntax, is added to remove custom syntax support from Rhai for applications that do not require it (which should be most).

• Comment lines beginning with //! (requires the metadata feature) are now collected as the script file's module documentation.
• AST and Module have methods to access and manipulate documentation.

• An API is added to automatically generate definition files from a fully-configured Engine, for use with the Rhai Language Server.

• switch cases can now include multiple values separated by |.
• Duplicated switch cases are now allowed.
• The error ParseErrorType::DuplicatedSwitchCase is deprecated.
• Ranges in switch statements that are small (currently no more than 16 items) are unrolled if possible.

• EvalContext::eval_expression_tree_raw and Expression::eval_with_context_raw are added to allow for not rewinding the Scope at the end of a statements block.
• A new range function variant that takes an exclusive range with a step.
• as_string is added to BLOB's to convert it into a string by interpreting it as a UTF-8 byte stream.
• FnAccess::is_private, FnAccess::is_public, FnNamespace::is_module_namespace and FnNameSpace::is_global_namespace are added for convenience.
• Iterator<Item=T> type for functions metadata is simplified to Iterator<T>.
• Scope::remove is added to remove a variable from a Scope, returning its value.
• The code base is cleaner by running it through Clippy.

• Self-contained AST now works properly with Engine::call_fn.
• Missing to_int from Decimal is added.
• Parsing of index expressions is relaxed and many cases no longer result in an index-type error to allow for custom indexers.
• Merging or combining a self-contained AST into another AST now works properly.
• Plugin modules/functions no longer generate errors under #![deny(missing_docs)].
• Calling a property on a function call that returns a shared value no longer causes an error.
• Strict Variables Mode now checks for module namespaces within functions as well.
• Module defined via Engine::register_static_module are now checked in Strict Variables Mode.

• ?, ??, ?., ?[ and !. are now reserved symbols.

• FnPtr::num_curried is deprecated in favor of FnPtr::curry().len().

• The Elvis operators (?. and ?[) are now supported for property access, method calls and indexing.
• The null-coalescing operator (??) is now supported to short-circuit () values.

• Indexing and property access are now faster.
• EvalAltResult::IndexNotFound is added to aid in raising errors for indexers.
• Engine::def_tag, Engine::def_tag_mut and Engine::set_tag are added to manage a default value for the custom evaluation state, accessible via EvalState::tag() (which is the same as NativeCallContext::tag()).
• Originally, the debugger's custom state uses the same state as EvalState::tag() (which is the same as NativeCallContext::tag()). It is now split into its own variable accessible under Debugger::state().
• Non-borrowed string keys can now be deserialized for object maps via serde.
• Scope::get is added to get a reference to a variable's value.
• Variable resolvers can now return a shared value which can be mutated.

• Compound assignments now work properly with indexers.
• Cloning a Scope no longer turns all constants to mutable.

• Strict Variables Mode no longer returns an error when an undeclared variable matches a variable/constant in the provided external Scope.

• The Engine::on_var and Engine::on_parse_token API's are now marked unstable/volatile.
• The closures passed to Engine::on_var, Engine::on_def_var and Engine::register_debugger take EvalContext instead of &EvalContext or &mut EvalContext.
• The following enum's are marked non_exhaustive: AccessMode, FnAccess, FnNamespace, FnMetadata, OptimizationLevel

• Module::eval_ast_as_new_raw is made public as a low-level API.
• format_map_as_json is provided globally, which is the same as to_json for object maps.
• Engine::call_fn_raw_raw is added to add speed to repeated function calls.
• Engine::eval_statements_raw is added to evaluate a sequence of statements.

• A custom state is provided that is persistent during the entire evaluation run. This custom state is a Dynamic, which can hold any data, and can be accessed by the host via EvalContext::tag, EvalContext::tag_mut, NativeCallContext::tag and GlobalRuntimeState.tag.

• Improper switch case condition syntax is now caught at parse time.
• Engine::parse_json now natively handles nested JSON inputs (using a token remap filter) without needing to replace { with #{.
• to_json is added to object maps to cheaply convert it to JSON format (() is mapped to null, all other data types must be supported by JSON)
• FileModuleResolver now accepts a custom Scope to provide constants for optimization.
• New variants, Start and End, are added to DebuggerEvent triggered at the start/end of script evaluation.

• Functions with Dynamic parameters now work in qualified calls from imported modules.
• rhai-repl now compiles with the new patch version of rustyline.
• rhai_codegen dependency is now explicitly 1.4 or higher.

• split now splits a string by whitespaces instead of splitting it into individual characters. This is more in line with common practices.
• A new function to_chars for strings is added to split the string into individual characters.

• Strings are now directly iterable (via for .. in) yielding individual characters.

This version, in particular, fixes a plugin macro hygiene error for the nightly compiler:

error[E0425]: cannot find value `args` in this scope

• Minimum compiler version is now 1.57 due to smartstring dependency.

• Fixed macro hygiene error with nightly compiler.
• Invalid property or method access such as a.b::c.d or a.b::func() no longer panics but properly returns a syntax error.
• Scope::is_constant now returns the correct value.
• Exporting a variable that contains a local function pointer (including anonymous function or closure) now raises a runtime error.
• Full optimization is now skipped for method calls.

• Type aliases in plugin modules are now used as friendly names for custom types. This makes plugin modules more self-contained when they are used to define a custom type's API.

• Variable definitions are optimized so that shadowed variables are reused as much as possible to reduce memory consumption.
• FnAccess and FnNamespace now implement Ord and PartialOrd.
• The event_handler_map example is enhanced to prevent shadowing of the state object map.
• Separation of constants in function calls is removed as its performance benefit is dubious.
• A function sleep is added to block the current thread by a specified number of seconds.
• Scope::set_alias is added to export a variable under a particular alias name.
• starts_with and ends_with are added for strings.
• Variables in modules registered via register_global_module can now be accessed in the global namespace.
• Dynamic::into_read_only is added to convert a Dynamic value into constant.
• Module now holds a collection of custom types with an API.

This version adds a debugging interface, which can be used to integrate a debugger.

Based on popular demand, an option is added to throw exceptions when invalid properties are accessed on object maps (default is to return ()).

Also based on popular demand, the REPL tool now uses a slightly-enhanced version of rustyline for line editing and history.

• In Scope::clone_visible, constants are now properly cloned as constants.
• Variables introduced inside try blocks are now properly cleaned up upon an exception.
• Off-by-one error in character positions after a comment line is now fixed.
• Globally-defined constants are now encapsulated correctly inside a loaded module and no longer spill across call boundaries.
• Type names display is fixed.
• Exceptions thrown inside function calls now unwrap correctly when catch-ed.
• Error messages for certain invalid property accesses are fixed.

• For consistency with the import statement, the export statement no longer exports multiple variables.
• Appending a BLOB to a string (via +, +=, append or string interpolation) now treats the BLOB as a UTF-8 encoded string.
• Appending a string/character to a BLOB (via += or append) now adds the string/character as a UTF-8 encoded byte stream.

• A debugging interface is added.
• A new bin tool, rhai-dbg (aka The Rhai Debugger), is added to showcase the debugging interface.
• A new package, DebuggingPackage, is added which contains the back_trace function to get the current call stack anywhere in a script.
• Engine::set_fail_on_invalid_map_property is added to control whether to raise an error (new EvalAltResult::ErrorPropertyNotFound) when invalid properties are accessed on object maps.
• Engine::set_allow_shadowing is added to allow/disallow variables shadowing, with new errors EvalAltResult::ErrorVariableExists and ParseErrorType::VariableExists.
• Engine::on_def_var allows registering a closure which can decide whether a variable definition is allow to continue, during compilation or runtime, or should fail with an error (ParseErrorType::ForbiddenVariable or EvalAltResult::ErrorForbiddenVariable).
• A new syntax for defining custom packages is introduced that removes the need to specify the Rhai crate name (internally uses the $crate meta variable).

• Default features for dependencies (such as ahash/std and num-traits/std) are no longer required.
• The no_module feature now eliminates large sections of code via feature gates.
• Debug display of AST is improved.
• NativeCallContext::call_level() is added to give the current nesting level of function calls.
• A new feature, bin-features, pulls in all the required features for bin tools.
• AST position display is improved:
  • Expr::start_position is added to give the beginning of the expression (not the operator's position).
  • StmtBlock and Stmt::Block now keep the position of the closing } as well.
• EvalAltResult::unwrap_inner is added to access the base error inside multiple layers of wrappings (e.g. EvalAltResult::ErrorInFunction).
• Yet another new syntax is introduced for def_package! that further simplifies the old syntax.
• A new method to_blob is added to convert a string into a BLOB as UTF-8 encoded bytes.
• A new method to_array is added to convert a BLOB into array of integers.

The REPL bin tool, rhai-rpl, has been enhanced.

• The rustyline feature is now required in order to build rhai-repl.
• Therefore, rhai-repl is no longer automatically built when using a simple cargo build with default features.

• rhai-repl now uses a modified version of rustyline as a line editor with history.
• Ctrl-Enter can now be used to enter multiple lines without having to attach the \ continuation character the end of each line.
• Bracketed paste is supported, even on Windows (version 10 or above), so pasting code directly into rhai-repl is made much more convenient.

• strict to turn on/off Strict Variables Mode.
• optimize to turn on/off script optimization.
• history to print lines history.
• !!, !num, !text and !?text to recall a history line.
• keys to print all key bindings.

This is primarily a bug-fix version which fixes a large number of bugs.

• Expressions such as x = x + 1 no longer panics.
• Padding arrays with another array via pad no longer loops indefinitely.
• chop for arrays and BLOB's now works properly.
• set_bit for bit-flags with negative index now works correctly.
• Misnamed params field name in the JSON output of Engine::gen_fn_metadata_to_json is fixed (was incorrectly named type).
• Fixes a potential unsafe violation in for loop.
• Missing to_hex, to_octal and to_binary for i128 and u128 are added.
• remove for arrays and BLOB's now treat negative index correctly.
• parse_int now works properly for negative numbers.
• Engine::gen_fn_signatures now generates signatures for external packages registered via Engine::register_global_module.
• \r\n pairs are now recognized correctly for doc-comments.

• Formatting of return types in functions metadata info is improved.
• Use SmartString for Scope variable names and remove unsafe lifetime casting.
• Functions in the standard library now have doc-comments (which can be obtained via Engine::gen_fn_metadata_to_json).
• get and set methods are added to arrays, BLOB's, object maps and strings.

This version adds support for integer ranges via the .. and ..= operators. Many standard API's are extended with range parameters where appropriate.

• is is (pun intended) now a reserved keyword to prepare for possible future type checking expressions (e.g. x is "string").

• LogicPackage is removed from CorePackage.
• Bit-field functions are moved into a new BitFieldPackage (used to be in LogicPackage) which makes more sense.

• Custom syntax now works properly inside binary expressions and with method calls.
• Hex numbers with the high-bit set now parse correctly into negative integer numbers.
• Constructing a literal array or object map now checks for size limits for each item instead of at the very end when it is already too late.
• Non-INT integer types are now treated exactly as custom types under only_i64 and only_i32.
• Calling pad on an array now checks for total size over limit after each item added.

• Added support for integer ranges via the .. and ..= operators.
• Added EvalAltResult::ErrorCustomSyntax to catch errors in custom syntax, which should not happen unless an AST is compiled on one Engine but evaluated on another unrelated Engine.

• BLOB's are refined to display in a more compact hex format.
• A new syntax is introduced for def_package! that will replace the old syntax in future versions.
• Added NativeCallContext::call_fn to easily call a function.
• Doc-comments on plugin module functions are extracted into the functions' metadata.

• Expression::get_variable_name is deprecated in favor of the new Expression::get_string_value.
• The old syntax of def_package! is deprecated in favor of the new syntax.

This version adds native support for BLOB's (byte arrays), as well as a number of configuration settings to fine-tun language features.

• Minimum compiler version is now 1.51.

• from_dynamic now supports deserializing Option.

• BLOB (essentially a byte array) is added as a supported primitive value type parallel to arrays.
• New options for Engine which allows disabling if-expressions, switch-expressions, statement expressions, anonymous functions and/or looping (i.e. while, loop, do and for statements):
  • Engine::set_allow_if_expression
  • Engine::set_allow_switch_expression
  • Engine::set_allow_statement_expression
  • Engine::set_allow_anonymous_fn
  • Engine::set_allow_looping
• New strict variables mode for Engine (enabled via Engine::set_strict_variables) to throw parse errors on undefined variable usage. Two new parse error variants, ParseErrorType::VariableNotFound and ParseErrorType::ModuleNotFound, are added.

• Two double quotes ("") in a string literal now maps to "; two back-ticks (``) in a literal string now maps to `.
• Added Engine::register_type_with_name_raw to register a custom type based on a fully-qualified type path.
• Added into_array and into_typed_array for Dynamic.
• Added FnPtr::call and FnPtr::call_within_context to simplify calling a function pointer.
• A function's hashes are included in its JSON metadata to assist in debugging. Each function's baseHash field in the JSON object should map directly to the pre-calculated hash in the function call.
• Expression now derefs to Expr.

• NativeCallContext::new is deprecated because it is simpler to call a function pointer via FnPtr::call.
• AST::merge_filtered and AST::combine_filtered are no longer exported under no_function.
• AST::new and AST::new_with_source are moved under internals.
• FnPtr::call_dynamic is deprecated in favor of FnPtr::call_raw.

• Array methods (such as map) taking a closure with captures as argument now works properly.

• As originally intended, function calls with a bang (!) now operates directly on the caller's scope, allowing variables inside the scope to be mutated.
• As originally intended, Engine::XXX_with_scope API's now properly propagate constants within the provided scope also to functions in the script.
• Printing of integral floating-point numbers is fixed (used to only prints 0.0).
• func!() calls now work properly under no_closure.
• Fixed parsing of unary negation such that expressions like if foo { ... } -x parses correctly.

• #[cfg(...)] attributes can now be put directly on plugin functions or function defined in a plugin module.
• A custom syntax parser can now return a symbol starting with $$ to inform the implementation function which syntax variant was actually parsed.
• AST::iter_literal_variables is added to extract all top-level literal constant/variable definitions from a script without running it.
• Engine::call_fn_dynamic is deprecated and Engine::call_fn_raw is added which allows keeping new variables in the custom scope.

• Array methods now avoid cloning as much as possible (although most predicates will involve cloning anyway if passed a closure).
• Array methods that take function pointers (e.g. closures) now optionally take the function name as a string.
• Array adds the dedup method.
• Array adds a sort method with no parameters which sorts homogeneous arrays of built-in comparable types (e.g. INT).
• Inlining is disabled for error-path functions because errors are exceptional and scripts usually fail completely when an error is encountered.
• The optimize module is completely eliminated under no_optimize, which should yield smaller code size.
• NativeCallContext::position is added to return the position of the function call.
• Scope::clone_visible is added that copies only the last instance of each variable, omitting all shadowed variables.

• NativeCallContext::call_fn_dynamic_raw is deprecated and NativeCallContext::call_fn_raw is added.
• From<EvalAltResult> for Result<T, Box<EvalAltResult> > is deprecated so it will no longer be possible to do EvalAltResult::ErrorXXXXX.into() to convert to a Result; instead, Err(EvalAltResult:ErrorXXXXX.into()) must be used. Code is clearer if errors are explicitly wrapped in Err.

• 0.0 now prints correctly (used to print 0e0).
• Unary operators are now properly recognized as an expression statement.
• Reverses a regression on string + operations.
• The global namespace is now searched before packages, which is the correct behavior.

• Assignment to indexing expression with dot expressions inside no longer cause a compilation error.
• The no_module and internals features now work together without a compilation error.
• String literal operations (such as "hello" + ", world") now optimizes correctly.

• Custom syntax starting with a disabled standard keyword now works properly.
• When calling Engine::call_fn, new variables defined during evaluation of the body script are removed and no longer spill into the function call.
• NamespaceRef::new is fixed.

• Engine::consume_XXX methods are renamed to Engine::run_XXX to make meanings clearer. The consume_XXX API is deprecated.
• Engine::register_type_XXX are now available even under no_object.
• Added Engine::on_parse_token to allow remapping certain tokens during parsing.
• Added Engine::const_empty_string to merge empty strings into a single instance.

• $symbol$ is supported in custom syntax to match any symbol.
• Custom syntax with $block$, } or ; as the last symbol are now self-terminating (i.e. no need to attach a terminating ;).

• Dynamic::as_string and Dynamic::as_immutable_string are deprecated and replaced by into_string and into_immutable_string respectively.
• Added a number of constants to Dynamic.
• Added a number of constants and fromXXX constant methods to Dynamic.
• Added sin, cos and tan for Decimal values.

• parse_float(), PI() and E() now defer to Decimal under no_float if decimal is turned on.
• Added log10() for Decimal.
• ln for Decimal is now checked and won't panic.

• SmartString now uses LazyCompact instead of Compact to minimize allocations.
• Added pop for strings.
• Added ImmutableString::ptr_eq to test if two strings point to the same allocation.
• The serde feature of SmartString is turned on under metadata to make Map serializable.

• Scope::set_value now takes anything that implements Into<Cow<str> >.
• Added Scope::is_constant to check if a variable is constant.
• Added Scope::set_or_push to add a new variable only if one doesn't already exist.

• Added ASTNode::position.
• ReturnType is removed in favor of option flags for Stmt::Return.
• Stmt::Break and Stmt::Continue are merged into Stmt::BreakLoop via an option flag.
• StaticVec is changed to keep three items inline instead of four.

• Eliminate unnecessary property write-back when accessed via a getter since property getters are assumed to be pure.
• Writing to a property of an indexed valued obtained via an indexer now works properly by writing back the changed value via an index setter.

• MultiInputsStream, ParseState, TokenIterator, IdentifierBuilder and AccessMode are exported under the internals feature.

• FloatWrapper is no longer erroneously exported under no_float+internals.
• The sign function now works properly for float values that are NaN.

• Fixed bug with catch variable used in catch block.

• Fixed bug in method call followed by an array indexing.

• Fixed bug in using indexing/dotting inside index bracket.
• while and loop statements are no longer considered pure (since a loop can go on forever and this is a side effect).

The official version 1.0.

Almost the same version as 0.20.3 but with deprecated API's removed.

• Fixed infinite loop in certain script optimizations.
• Building for no-std no longer requires patching smartstring.
• Parsing a lone return or throw without a semicolon at the end of a block no longer raises an error.

• All deprecated API's (e.g. the RegisterFn and RegisterResultFn traits) are removed.
• Module::set_id is split into Module::set_id and Module::clear_id pair.
• begin, end, each, then, unless are no longer reserved keywords.

• New methods is_odd, is_even for integers, and is_zero for all numbers.
• From<BTreeSet> and From<HashSet> are added for Dynamic, which create object maps with () values.

This version adds support to index into an integer number, treating it as a bit-field.

• Fixed incorrect optimization regarding chain-indexing with non-numeric index.
• Variable values are checked for over-sized violations after assignments and setters.

• To keep the API consistent, strings are no longer iterable by default. Use the chars method to iterate through the characters in a string.
• Dynamic::take_string and Dynamic::take_immutable_string are renamed to Dynamic::as_string and Dynamic::as_immutable_string respectively.

• New syntax for for statement to include counter variable.
• An integer value can now be indexed to get/set a single bit.
• The bits method of an integer can be used to iterate through its bits.
• New $bool$, $int$, $float$ and $string$ expression types for custom syntax.
• New methods to_hex, to_octal and to_binary for integer numbers.
• New methods to_upper, to_lower, make_upper, make_lower for strings/characters.

This version adds a number of convenience features:

• Ability for a Dynamic to hold an i32 tag of arbitrary data

• Simplifies dynamic properties access by falling back to an indexer (passing the name of the property as a string) when a property is not found.

• Propagation of constants held in a custom scope now works properly instead of always replacing by ().

• Engine::disable_doc_comments is removed because doc-comments are now placed under the metadata feature flag.
• Registering a custom syntax now only requires specifying whether the Scope is adjusted (i.e. whether variables are added or removed). There is no need to specify the number of variables added/removed.
• Assigning to a property of a constant is now allowed and no longer raise an EvalAltResult::ErrorAssignmentToConstant error. This is to facilitate the Singleton pattern. Registered setter functions are automatically guarded against setters calling on constants and will continue to raise errors unless the pure attribute is present (for plugins).
• If a property getter/setter is not found, an indexer with string index, if any, is tried.
• The indexers API (Engine::register_indexer_XXX and Module::set_indexer_XXX) are now also exposed under no_index.

• Each Dynamic value can now contain arbitrary data (type i32) in the form of a tag. This is to use up otherwise wasted space in the Dynamic type.
• A new internal feature no_smartstring to turn off SmartString for those rare cases that it is needed.
• DynamicReadLock and DynamicWriteLoc are exposed under internals.
• From< Shared< Locked<Dynamic> > > is added for Dynamic mapping directly to a shared value, together with support for Dynamic::from.
• An indexer with string index acts as a fallback to a property getter/setter.

• Registering a custom syntax now only requires specifying whether the Scope is adjusted (i.e. whether variables are added or removed). This allows more flexibility for cases where the number of new variables declared depends on internal logic.
• Putting a pure attribute on a plugin property/index setter now enables it to be used on constants.

This version enables functions to access constants declared at global level via the special global module.

• Fixed bug when position is zero in insert and split_at methods for arrays.
• Indexing operations with pure index values are no longer considered pure due to the possibility of indexers.

• Dynamic::is_shared and Dynamic::is_locked are removed under the no_closure feature. They used to always return false.
• Engine::call_fn now evaluates the AST before calling the function.
• Engine::on_progress is disabled with unchecked.

• The crate no-std-compat is used to compile for no-std. This removes the need to use a special crate::stdlib namespace for std imports.

• A module called global is automatically created to hold global-level constants, which can then be accessed from functions.
• A new feature no_position is added to turn off position tracking during parsing to squeeze out the last drop of performance.

This version adds string interpolation with `... ${ ... } ...` syntax.

switch statement cases can now have conditions.

Negative indices for arrays and strings are allowed and now count from the end (-1 = last item/character).

• Property setter op-assignments now work properly.
• Off-by-one bug in Array::drain method with range is fixed.

• Negative index to an array or string yields the appropriate element/character counting from the end.
• The default _ case of a switch statement now must be the last case, together with two new error variants: EvalAltResult::WrongSwitchDefaultCase and EvalAltResult::WrongSwitchCaseCondition.
• ModuleResolver trait methods take an additional parameter source_path that contains the path of the current environment. This is to facilitate loading other script files always from the current directory.
• FileModuleResolver now resolves relative paths under the source path if there is no base path set.
• FileModuleResolver::base_path now returns Option<&str> which is None if there is no base path set.
• Doc-comments now require the metadata feature.

• Array::drain and Array::retain methods with predicate now scan the array in forward order instead of in reverse.

• String interpolation support is added via the `... ${ ... } ...` syntax.
• FileModuleResolver resolves relative paths under the parent path (i.e. the path holding the script that does the loading). This allows seamless cross-loading of scripts from a directory hierarchy instead of having all relative paths load from the current working directory.
• Negative index to an array or string yields the appropriate element/character counting from the end.
• switch statement cases can now have an optional if clause.

This version replaces all internal usage of HashMap with BTreeMap, which should result in some speed improvement because a BTreeMap is leaner when the number of items held is small. Most, if not all, collections in Rhai hold very few data items, so this is a typical scenario of many tiny-sized collections.

The Rhai object map type, Map, used to be an alias to HashMap and is now aliased to BTreeMap instead. This is also because, in the vast majority of usage cases, the number of properties held by an object map is small.

HashMap and BTreeMap have almost identical public API's so this change is unlikely to break existing code.

SmartString is used to store identifiers (which tend to be short, fewer than 23 characters, and ASCII-based) because they can usually be stored inline. Map keys now also use SmartString.

In addition, there is now support for line continuation in strings (put \ at the end of line) as well as multi-line literal strings (wrapped by back-ticks: `...`).

Finally, all function signature/metadata methods are now grouped under the umbrella metadata feature. This avoids spending precious resources maintaining metadata for functions for the vast majority of use cases where such information is not required.

• The feature flags no_index + no_object now compile without errors.

• The traits RegisterFn and RegisterResultFn are removed. Engine::register_fn and Engine::register_result_fn are now implemented directly on Engine.
• FnPtr::call_dynamic now takes &NativeCallContext instead of consuming it.
• All Module::set_fn_XXX methods are removed, in favor of Module::set_native_fn.
• Array::reduce and Array::reduce_rev now take a Dynamic as initial value instead of a function pointer.
• protected, super are now reserved keywords.
• The Module::set_fn_XXX API now take &str as the function name instead of Into<String>.
• The reflections API such as Engine::gen_fn_signatures, Module::update_fn_metadata etc. are put under the metadata feature gate.
• The shebang #! is now a reserved symbol.
• Shebangs at the very beginning of script files are skipped when loading them.
• SmartString is used for identifiers by default. Currently, a PR branch is pulled for no-std builds. The official crate will be used once SmartString is fixed to support no-std.
• Map is now an alias to BTreeMap<SmartString, Dynamic> instead of HashMap because most object maps hold few properties.
• EvalAltResult::FnWrongDefinition is renamed WrongFnDefinition for consistency.

• Line continuation (via \) and multi-line literal strings (wrapped with `) support are added.
• Rhai scripts can now start with a shebang #! which is ignored.

• Replaced all HashMap usage with BTreeMap for better performance because collections in Rhai are tiny.
• Engine::register_result_fn no longer requires the successful return type to be Dynamic. It can now be any clonable type.
• #[rhai_fn(return_raw)] can now return Result<T, Box<EvalAltResult> > where T is any clonable type instead of Result<Dynamic, Box<EvalAltResult> >.
• Dynamic::clone_cast is added to simplify casting from a &Dynamic.

This version runs faster due to optimizations done on AST node structures. It also fixes a number of panic bugs related to passing shared values as function call arguments.

• Panic when passing a shared string into a registered function as &str argument is fixed.
• Panic when calling switch statements on custom types is fixed.
• Potential overflow panics in range(from, to, step) is fixed.
• &mut String parameters in registered functions no longer panic when passed a string.
• Some expressions involving shared variables now work properly, for example x in shared_value, return shared_value, obj.field = shared_value etc. Previously, the resultant value is still shared which is counter-intuitive.
• Errors in native Rust functions now contain the correct function call positions.
• Fixed error types in EvalAltResult::ErrorMismatchDataType which were swapped.

• Dynamic::as_str is removed because it does not properly handle shared values.
• Zero step in the range function now raises an error instead of creating an infinite stream.
• Error variable captured by catch is now an object map containing error fields.
• EvalAltResult::clear_position is renamed EvalAltResult::take_position and returns the position taken.
• private functions in an AST can now be called with call_fn etc.
• NativeCallContext::call_fn_dynamic_raw no longer has the pub_only parameter.
• Module::update_fn_metadata input parameter is changed.
• Function keywords (e.g. type_of, eval, Fn) can no longer be overloaded. It is more trouble than worth. To disable these keywords, use Engine::disable_symbol.
• is_def_var and is_def_fn are now reserved keywords.
• Engine::id field is removed because it is never used.
• num-traits is now a required dependency.
• The in operator is now implemented on top of the contains function and is no longer restricted to a few specific types.
• EvalAltResult::ErrorInExpr is removed because the in operator now calls contains.
• The methods AST::walk, Expr::walk, Stmt::walk and ASTNode::walk and the callbacks they take now return bool to optionally terminate the recursive walk.

• Layout of AST nodes is optimized to reduce redirections, so speed is improved.
• Function calls are more optimized and should now run faster.
• range function now supports negative step and decreasing streams (i.e. to < from).
• More information is provided to the error variable captured by the catch statement in an object map.
• Previously, private functions in an AST cannot be called with call_fn etc. This is inconvenient when trying to call a function inside a script which also serves as a loadable module exporting part (but not all) of the functions. Now, all functions (private or not) can be called in an AST. The private keyword is relegated to preventing a function from being exported.
• Dynamic::as_unit just for completeness sake.
• bytes method added for strings to get length quickly (if the string is ASCII-only).
• FileModuleResolver can now enable/disable caching.
• Recursively walking an AST can now be terminated in the middle.

This version introduces functions with Dynamic parameters acting as wildcards.

• Bug in Position::is_beginning_of_line is fixed.

• For plugin functions, constants passed to methods (i.e. &mut parameter) now raise an error unless the functions are marked with #[rhai_fn(pure)].
• Visibility (i.e. pub or not) for generated plugin modules now follow the visibility of the underlying module.
• Comparison operators between the sames types or different numeric types now throw errors when they're not defined instead of returning the default. Only comparing between different types will return the default.
• Default stack-overflow and top-level expression nesting limits for release builds are lowered to 64 from 128.
• Engine::call_fn_dynamic takes an additional parameter to optionally evaluate the given AST before calling the function.

• Functions are now allowed to have Dynamic arguments.
• #[rhai_fn(pure)] attribute to mark a plugin function with &mut parameter as pure so constants can be passed to it. Without it, passing a constant value into the &mut parameter will now raise an error.

• Built-in operators between FLOAT/Decimal and INT are now implemented for more speed under those cases.
• Error position in eval statements is now wrapped in an EvalAltResult::ErrorInFunctionCall.
• Position now implements Add and AddAssign.
• Scope now implements IntoIterator.
• Strings now have the -/-= operators and the remove method to delete a sub-string/character.
• Strings now have the split_rev method and variations of split with maximum number of segments.
• Arrays now have the split method.
• Comparisons between FLOAT/Decimal and INT are now built in.
• Comparisons between string and char are now built in.
• Engine::call_fn_dynamic can now optionally evaluate the given AST before calling the function.

This version is an incremental release with a number of enhancements and bug fixes.

Notice that there are a number of breaking changes, especially with regards to replacing the ~ exponential operator with **, and the addition of the decimal feature that turns on Decimal support.

• Empty statements (i.e. statements with only one ;) now parse correctly and no longer hang.
• continue, break and return statements no longer panic inside a try .. catch block.
• round function for f64 is now implemented correctly.

• In order to be consistent with other scripting languages:
  • the power/exponentiation operator is changed from ~ to **; ~ is now a reserved symbol
  • the power/exponentiation operator now binds to the right
  • trigonometry functions now take radians and return radians instead of degrees
• Dynamic::into_shared is no longer available under no_closure. It used to panic.
• Token::is_operator is renamed to Token::is_symbol.
• AST::clone_functions_only_filtered, AST::merge_filtered, AST::combine_filtered and AST::retain_functions now take Fn instead of FnMut as the filter predicate.

• Scientific notation is supported for floating-point number literals.
• A new feature, decimal, enables the Decimal data type. When both no_float and decimal features are enabled, floating-point literals parse to Decimal.

• Functions resolution cache is used in more cases, making repeated function calls faster.
• Added atan(x, y) and hypot(x, y) to BasicMathPackage.
• Added standard arithmetic operators between FLOAT/Decimal and INT.

This version streamlines compiling for WASM.

Rust compiler minimum version is raised to 1.49.

• Parameters passed to plugin module functions were sometimes erroneously consumed. This is now fixed.
• Fixes compilation errors in metadata feature build.
• Stacking ! operators now work properly.
• Off-by-one error in insert method for arrays is fixed.
• Invalid property access now throws the appropriate error instead of panics.

• Rust compiler requirement raised to 1.49.
• NativeCallContext::new taker an additional parameter containing the name of the function called.
• Engine::set_doc_comments is renamed Engine::enable_doc_comments.

• Two new features, wasm-bindgen and stdweb, to specify the JS interop layer for WASM builds. wasm-bindgen used to be required.

• ahash is used to hash function call parameters. This should yield speed improvements.
• Dynamic and ImmutableString now implement serde::Serialize and serde::Deserialize.
• NativeCallContext has a new field containing the name of the function called, useful when the same Rust function is registered under multiple names in Rhai.
• New functions PI() and E() to return mathematical constants, and to_radians and to_degrees to convert between radians and degrees.

• no_std feature now compiles correctly (bug introduced in 0.19.9).
• Bug in FileModuleResolver::clear_cache_for_path path mapping fixed.
• Some optimizer fringe cases are fixed - related to constants propagation when the evil eval is present.

• The error variant EvalAltResult::ErrorInFunctionCall has a new parameter holding the source of the function.
• ParseErrorType::WrongFnDefinition is renamed FnWrongDefinition.
• Redefining an existing function within the same script now throws a new ParseErrorType::FnDuplicatedDefinition. This is to prevent accidental overwriting an earlier function definition.
• AST::set_source is now split into AST::set_source and AST::clear_source.

• Engine::compile_into_self_contained compiles a script into an AST and eagerly resolves all import statements with string literal paths. The resolved modules are directly embedded into the AST. When the AST is later evaluated, import statements directly yield the pre-resolved modules without going through the resolution process once again.
• AST::walk, Stmt::walk and Expr::walk internal API's to recursively walk an AST.

• Source information is provided when there is an error within a call to a function defined in another module.
• Source information is provided to the NativeCallContext for native Rust functions.
• EvalAltResult::clear_position to clear the position information of an error - useful when only the message is needed and the position doesn't need to be printed out.
• A new optional function resolve_ast is added to the ModuleResolver trait for advanced usage.

This version fixes a bug introduced in 0.19.8 which breaks property access within closures.

It also removes the confusing differences between packages and modules by unifying the terminology and API under the global umbrella of modules.

• Fix bug when accessing properties in closures.
• Fix bug when accessing a deep index with a function call.
• Fix bug that sometimes allow assigning to an invalid l-value.
• Fix off-by-one error with Engine::set_max_call_levels.

• Engine::load_package is renamed Engine::register_global_module and now must explicitly pass a shared [Module].
• Engine::register_module is renamed Engine::register_static_module and now must explicitly pass a shared [Module].
• Package::get is renamed Package::as_shared_module.
• Engine::set_module_resolver now takes a straight module resolver instead of an Option. To disable module resolving, use the new DummyModuleResolver.

• Scope is now Clone + Hash.
• Engine::register_static_module now supports sub-module paths (e.g. foo::bar::baz).
• Engine::register_custom_operator now accepts reserved symbols.
• Engine::register_custom_operator now returns an error if given a precedence of zero.
• The examples repl and rhai_runner are moved into bin and renamed rhai-repl and rhai-run respectively.

This version makes it easier to generate documentation for a Rhai code base.

Each function defined in an AST can optionally attach doc-comments (which, as in Rust, are comments prefixed by either /// or /**). Doc-comments allow third-party tools to automatically generate documentation for functions defined in a Rhai script.

A new API, Engine::gen_fn_metadata_to_json and Engine::gen_fn_metadata_with_ast_to_json, paired with the new metadata feature, exports the full list of functions metadata (including those in an AST) as a JSON document.

There are also a sizable number of bug fixes.

• Unary prefix operators -, + and ! now bind correctly when applied to an expression. Previously, -x.len is parsed as (-x).len which is obviously counter-intuitive.
• Indexing of namespace-qualified variables now work properly, such as path::to::var[x].
• Constants are no longer propagated by the optimizer if shadowed by a non-constant variable.
• A constant passed as the this parameter to Rhai functions now throws an error if assigned to.
• Generic type parameter of Engine::register_iterator is IntoIterator instead of Iterator.
• Fixes parsing of block comments ending with **/ or inner blocks starting with //*.

• Engine::on_progress now takes u64 instead of &u64.
• The closure for Engine::on_debug now takes two additional parameters: source: Option<&str> and pos: Position.
• AST::iter_functions now returns ScriptFnMetadata.
• The parser function passed to Engine::register_custom_syntax_raw now takes an additional parameter containing the look-ahead symbol.

• AST::iter_functions now returns ScriptFnMetadata which includes, among others, doc-comments for functions prefixed by /// or /**.
• Doc-comments can be enabled/disabled with the new Engine::set_doc_comments method.
• A new feature metadata is added that pulls in serde_json and enables Engine::gen_fn_metadata_to_json and Engine::gen_fn_metadata_with_ast_to_json which exports the full list of functions metadata (including those inside an AST) in JSON format.
• Engine::on_debug provides two additional parameters: source: Option<&str> and pos: Position, containing the current source (if any) and position of the debug statement.
• NativeCallContext and EvalContext both expose source() which returns the current source, if any.

• A functions lookup cache is added to make function call resolution faster.
• Capturing a constant variable in a closure is now supported, with no cloning.
• A look-ahead symbol is provided to custom syntax parsers, which can be used to parse variable-length symbol streams.

• Fixes compilation errors with certain feature flag combinations.

• Property getters/setters and indexers defined in a plugin module are by default #[rhai_fn(global)].
• to_debug is a new standard function for converting a value into debug format.
• Arrays and object maps now print values using to_debug (if available).

This version adds the switch statement.

It also allows exposing selected module functions (usually methods) to the global namespace. This is very convenient when encapsulating the API of a custom Rust type into a module while having methods and iterators registered on the custom type work normally.

A new gen_fn_signatures API enables enumerating the registered functions of an Engine for documentation purposes. It also prepares the way for a future reflection API.

• Custom syntax that introduces a shadowing variable now works properly.

• Module::set_fn, Module::set_raw_fn and Module::set_fn_XXX_mut all take an additional parameter of FnNamespace.
• Module::set_fn takes a further parameter with a list of parameter names/types plus the function return type, if any.
• Module::get_sub_module_mut is removed.
• begin, end, unless are now reserved keywords.
• EvalPackage is removed in favor of Engine::disable_symbol.

• New switch statement.
• New do ... while and do ... until statements.
• New Engine::gen_fn_signatures, Module::gen_fn_signatures and PackagesCollection::gen_fn_signatures to generate a list of signatures for functions registered.
• New Engine::register_static_module to register a module as a sub-module in the global namespace.
• New set_exported_global_fn! macro to register a plugin function and expose it to the global namespace.
• Module::set_fn_XXX_mut can expose a module function to the global namespace. This is convenient when registering an API for a custom type.
• Module::set_getter_fn, Module::set_setter_fn, Module::set_indexer_get_fn, Module::set_indexer_set_fn all expose the function to the global namespace by default. This is convenient when registering an API for a custom type.
• New Module::update_fn_metadata to update a module function's parameter names and types.
• New #[rhai_fn(global)] and #[rhai_fn(internal)] attributes to determine whether a function defined in a plugin module should be exposed to the global namespace. This is convenient when defining an API for a custom type.
• New get_fn_metadata_list to get the metadata of all script-defined functions in scope.

• New constants under Dynamic including UNIT, TRUE, FALSE, ZERO, ONE etc.
• Floating-point numbers ending with a decimal point without a trailing 0 are supported.

This version fixes a bug that prevents compilation with the internals feature. It also speeds up importing modules.

• Fixes compilation error when using the internals feature. Bug introduced in 0.19.4.
• Importing script files recursively no longer panics.

• Modules imported at global level can now be accessed in functions.
• ModuleResolver::resolve now returns Shared<Module> for better resources sharing when loading modules.
• ParseErrorType::DuplicatedExport is removed as multiple export's are now allowed.

• Modules imported via import statements at global level can now be used in functions. There is no longer any need to re-import the modules at the beginning of each function block.
• Modules imported via import statements are encapsulated into the AST when loading a module from a script file.
• export keyword can now be tagged onto let and const statements as a short-hand, e.g.: export let x = 42;
• Variables can now be export-ed multiple times under different names.
• index_of, == and != are defined for arrays.
• == and != are defined for object maps.

This version basically cleans up the code structure in preparation for a potential 1.0 release in the future. Most scripts should see a material speed increase.

This version also adds a low-level API for more flexibility when defining custom syntax.

• Fixes Send + Sync for EvalAltResult under the sync feature. Bug introduced with 0.19.3.

• Custom syntax can no longer start with a keyword (even a reserved one), even if it has been disabled. That is to avoid breaking scripts later when the keyword is no longer disabled.

• EvalAltResult::ErrorAssignmentToUnknownLHS is moved to ParseError::AssignmentToInvalidLHS. ParseError::AssignmentToCopy is removed.
• EvalAltResult::ErrorDataTooLarge is simplified.
• Engine::on_progress closure signature now returns Option<Dynamic> with the termination value passed on to EvalAltResult::ErrorTerminated.
• ParseErrorType::BadInput now wraps a LexError instead of a text string.

• f32_float feature to set FLOAT to f32.
• Low-level API for custom syntax allowing more flexibility in designing the syntax.
• Module::fill_with to poly-fill a module with another.
• Scripts terminated via Engine::on_progress can now pass on a value as a termination token.

• Essential AST structures like Expr and Stmt are packed into smaller sizes (16 bytes and 32 bytes on 64-bit), stored inline for more cache friendliness, and de-Boxed as much as possible.
• Scope is optimized for cache friendliness.

This version streamlines some of the advanced API's, and adds the try ... catch statement to catch exceptions.

• EvalAltResult::ErrorReadingScriptFile is removed in favor of the new EvalAltResult::ErrorSystem.
• EvalAltResult::ErrorLoopBreak is renamed to EvalAltResult::LoopBreak.
• Engine::register_raw_fn and FnPtr::call_dynamic function signatures have changed.
• Callback signatures to Engine::on_var and Engine::register_custom_syntax have changed.
• EvalAltResult::ErrorRuntime now wraps a Dynamic instead of a string.
• Default call stack depth for debug builds is reduced to 8 (from 12) because it keeps overflowing the stack in GitHub CI!
• Keyword thread is reserved.

• The plugins system is enhanced to support functions taking a NativeCallContext as the first parameter.
• throw statement can now throw any value instead of just text strings.
• New try ... catch statement to catch exceptions.

• Calling eval or Fn in method-call style, which is an error, is now caught during parsing.
• func!() call style is valid even under no_closure feature.

Bug fix on call module functions.

This version adds a variable resolver with the ability to short-circuit variable access, plus a whole bunch of array methods.

• AST::iter_functions now returns an iterator instead of taking a closure.
• Module::get_script_function_by_signature renamed to Module::get_script_fn and returns &<Shared<ScriptFnDef> >.
• Module::num_fn, Module::num_var and Module::num_iter are removed and merged into Module::count.
• The merge_namespaces parameter to Module::eval_ast_as_new is removed and now defaults to true.
• GlobalFileModuleResolver is removed because its performance gain over the FileModuleResolver is no longer very significant.
• The following EvalAltResult variants are removed and merged into EvalAltResult::ErrorMismatchDataType: ErrorCharMismatch, ErrorNumericIndexExpr, ErrorStringIndexExpr, ErrorImportExpr, ErrorLogicGuard, ErrorBooleanArgMismatch
• Scope::iter_raw returns an iterator with an additional field indicating whether the variable is constant or not.
• rhai::ser and rhai::de namespaces are merged into rhai::serde.
• New reserved symbols: ++, --, .., ....
• Callback signature for custom syntax implementation function is changed to allow for more flexibility.
• Default call stack depth for debug builds is reduced to 12 (from 16).
• Precedence for ~ is raised, while in is moved below logic comparison operators.

• New Engine::on_var to register a variable resolver.
• const statements can now take any expression (or none at all) instead of only constant values.
• OptimizationLevel::Simple now eagerly evaluates built-in binary operators of primary types (if not overloaded).
• is_def_var() to detect if variable is defined, and is_def_fn() to detect if script function is defined.
• Dynamic::from(&str) now constructs a Dynamic with a copy of the string as value.
• AST::combine and AST::combine_filtered allows combining two AST's without creating a new one.
• map, filter, reduce, reduce_rev, some, all, extract, splice, chop and sort functions for arrays.
• New Module::set_iterable and Module::set_iterator to define type iterators more easily. Engine::register_iterator is changed to use the simpler version.

• Many one-liners and few-liners are now marked #[inline] or [inline(always)], just in case it helps when LTO is not turned on.

The major new feature for this version is Plugins support, powered by procedural macros. Plugins make it extremely easy to develop and register Rust functions with an Engine.

• if statement with an empty true block would not evaluate the false block. This is now fixed.
• Fixes a bug in Module::set_fn_4_mut.
• Module API's now properly handle &str and String parameters.
• Indexers are available under no_object.
• Registered operator-assignment functions (e.g. +=) now work correctly.

• Engine::register_set_result and Engine::register_indexer_set_result now take a function that returns Result<(), Box<EvalAltResult> >.
• Engine::register_indexer_XXX and Module::set_indexer_XXX panic when the type is Array, Map or String.
• EvalAltResult has a new variant ErrorInModule which holds errors when loading an external module.
• Module::eval_ast_as_new now takes an extra boolean parameter, indicating whether to encapsulate the entire module into a separate namespace.
• Functions in FileModuleResolver loaded modules now can cross-call each other in addition to functions in the global namespace. For the old behavior, use MergingFileModuleResolver instead.
• New EvalAltResult::ErrorInModule variant capturing errors when loading a module from a script file.

• Plugins support via procedural macros.
• Scripted functions are allowed in packages.
• parse_int and parse_float functions for parsing numbers; split function for splitting strings.
• AST::iter_functions and Module::iter_script_fn_info to iterate functions.
• Functions iteration functions for AST and Module now take FnMut instead of Fn.
• New FileModuleResolver that encapsulates the entire AST of the module script, allowing function cross-calling. The old version is renamed MergingFileModuleResolver.
• + and - operators for timestamps to increment/decrement by seconds.

• Engine::compile_expression, Engine::eval_expression etc. no longer parse anonymous functions and closures.
• Imported modules now work inside closures.
• Closures that capture now work under no_object.

• Adds Module::combine_flatten to combine two modules while flattening to the root level.

• Fixes bug that prevents calling functions in closures.
• Fixes bug that erroneously consumes the first argument to a namespace-qualified function call.

• Module::contains_fn and Module::get_script_fn no longer take the public_only parameter.

• Adds Engine::register_get_result, Engine::register_set_result, Engine::register_indexer_get_result, Engine::register_indexer_set_result API.
• Adds Module::combine to combine two modules.
• Engine::parse_json now also accepts a JSON object starting with #{.

This version adds:

• Anonymous functions (in Rust closure syntax). Simplifies creation of single-use ad-hoc functions.
• Currying of function pointers.
• Closures - auto-currying of anonymous functions to capture shared variables from the external scope. Use the no_closure feature to disable sharing values and capturing.
• Binding the this pointer in a function pointer call.
• Capturing call scope via func!(...) syntax.

• call can now be called function-call style for function pointers - this is to handle builds with no_object.
• Reserve language keywords, such as print, eval, call, this etc.
• x.call(f, ...) allows binding x to this for the function referenced by the function pointer f.
• Anonymous functions are supported in the syntax of a Rust closure, e.g. |x, y, z| x + y - z.
• Custom syntax now works even without the internals feature.
• Currying of function pointers is supported via the new curry keyword.
• Automatic currying of anonymous functions to capture shared variables from the external scope.
• Capturing of the calling scope for function call via the func!(...) syntax.
• Module::set_indexer_get_set_fn is added as a short-hand of both Module::set_indexer_get_fn and Module::set_indexer_set_fn.
• New unicode-xid-ident feature to allow Unicode Standard Annex #31 for identifiers.
• Scope::iter_raw returns an iterator with a reference to the underlying Dynamic value (which may be shared).

• Language keywords are now reserved (even when disabled) and they can no longer be used as variable names.
• Function signature for defining custom syntax is simplified.
• Engine::register_raw_fn_XXX API shortcuts are removed.
• PackagesCollection::get_fn, PackagesCollection::contains_fn, Module::get_fn and Module::contains_fn now take an additional public_only parameter indicating whether only public functions are accepted.
• The iterator returned by Scope::iter now contains a clone of the Dynamic value (unshared).
• Engine::register_global_module takes any type that is Into<PackageLibrary>.
• Error in Engine::register_custom_syntax is no longer Box-ed.

• Most compilation warnings are eliminated via feature gates.

This version adds:

• serde support for working with Dynamic values (particularly object maps).
• Low-level API to register functions.
• Surgically disable keywords and/or operators in the language.
• Define custom operators.
• Extend the language via custom syntax.

• Fixed method calls in the middle of a dot chain.

• EvalAltResult::ErrorMismatchOutputType has an extra argument containing the name of the requested type.
• Engine::call_fn_dynamic take an extra argument, allowing a Dynamic value to be bound to the this pointer.
• Precedence of the % (modulo) operator is lowered to below bit shifts. This is to handle the case of x < < 3 % 10.

• New serde feature to allow serializing/deserializing to/from Dynamic values using serde. This is particularly useful when converting a Rust struct to a Dynamic object map and back.
• Engine::disable_symbol to surgically disable keywords and/or operators.
• Engine::register_custom_operator to define a custom operator.
• Engine::register_custom_syntax to define a custom syntax.
• New low-level API Engine::register_raw_fn.
• New low-level API Module::set_raw_fn mirroring Engine::register_raw_fn.
• AST::clone_functions_only, AST::clone_functions_only_filtered and AST::clone_statements_only to clone only part of an AST.
• The boolean ^ (XOR) operator is added.
• FnPtr is exposed as the function pointer type.
• rhai::module_resolvers::ModuleResolversCollection added to try a list of module resolvers.
• It is now possible to mutate the first argument of a namespace-qualified function call when the argument is a simple variable (but not a module constant).
• Many configuration/setting API's now returns &mut Self so that the calls can be chained.
• String parameters in functions are supported (but inefficiently).

Bug fix release to fix errors when compiling with features.

The major new feature in this version is OOP - well, poor man's OOP, that is.

The README is officially transferred to The Rhai Book.

An online Playground is available.

• The trait function ModuleResolver::resolve no longer takes a Scope as argument.
• Functions defined in script now differentiates between using method-call style and normal function-call style. The method-call style will bind the object to the this parameter instead of consuming the first parameter.
• Imported modules are no longer stored in the Scope. Scope::push_module is removed. Therefore, cannot rely on module imports to persist across invocations using a Scope.
• AST::retain_functions is used for another purpose. The old AST::retain_functions is renamed to AST::clear_statements.

• Support for function pointers via Fn(name) and Fn.call(...) syntax - a poor man's first-class function.
• Support for calling script-defined functions in method-call style with this binding to the object.
• Special support in object maps for OOP.
• Expanded the AST API for fine-tuned manipulation of functions.

• The Rhai Book is online. Most content in the original README was transferred to the Book.
• New feature internals to expose internal data structures (e.g. the AST nodes).

This is a minor release which enables updating indexers (via registered indexer setters) and supports functions with &str parameters (maps transparently to ImmutableString). WASM is also a tested target.

• let s="abc"; s[1].change_to('X'); now correctly sets the character 'X' into 's' yielding "aXc".

• Callback closure passed to Engine::on_progress now takes &u64 instead of u64 to be consistent with other callback signatures.
• Engine::register_indexer is renamed to Engine::register_indexer_get.
• Module::set_indexer_fn is renamed to Module::set_indexer_get_fn.
• The tuple ParseError now exposes the internal fields and the ParseError::error_type and ParseError::position methods are removed. The first tuple field is the ParseErrorType and the second tuple field is the Position.
• Engine::call_fn_dynamic now takes any type that implements IntoIterator<Item = Dynamic>.

• Indexers are now split into getters and setters (which now support updates). The API is split into Engine::register_indexer_get and Engine::register_indexer_set with Engine::register_indexer_get_set being a short-hand. Similarly, Module::set_indexer_get_fn and Module::set_indexer_set_fn are added.
• Engine:register_fn and Engine:register_result_fn accepts functions that take parameters of type &str (immutable string slice), which maps directly to ImmutableString. This is to avoid needing wrappers for functions taking string parameters.
• Set maximum limit on data sizes: Engine::set_max_string_size, Engine::set_max_array_size and Engine::set_max_map_size.
• Supports trailing commas on array literals, object map literals, function definitions and function calls.
• Enhances support for compiling to WASM.

This version uses immutable strings (ImmutableString type) and built-in operator functions (e.g. +, >, +=) to improve speed, plus some bug fixes.

• Do not optimize script with eval_expression - it is assumed to be one-off and short.

• Indexing with an index or dot expression now works property (it compiled wrongly before). For example, let s = "hello"; s[s.len-1] = 'x'; now works property instead of causing a runtime error.
• if expressions are not supposed to be allowed when compiling for expressions only. This is fixed.

• Engine::compile_XXX functions now return ParseError instead of Box<ParseError>.
• The RegisterDynamicFn trait is merged into the RegisterResultFn trait which now always returns RhaiResult.
• Default maximum limit on levels of nested function calls is fine-tuned and set to a different value.
• Some operator functions are now built in (see Speed enhancements below), so they are available even under Engine::new_raw.
• Strings are now immutable. The type rhai::ImmutableString is used instead of std::string::String. This is to avoid excessive cloning of strings. All native-Rust functions taking string parameters should switch to rhai::ImmutableString (which is either Rc<String> or Arc<String> depending on whether the sync feature is used).
• Native Rust functions registered with the Engine also mutates the first argument when called in normal function-call style (previously the first argument will be passed by value if not called in method-call style). Of course, if the first argument is a calculated value (e.g. result of an expression), then mutating it has no effect, but at least it is not cloned.
• Some built-in methods (e.g. len for string, floor for FLOAT) now have property versions in addition to methods to simplify coding.

• Set limit on maximum level of nesting expressions and statements to avoid panics during parsing.
• New EvalPackage to disable eval.
• Module::set_getter_fn, Module::set_setter_fn and Module:set_indexer_fn to register getter/setter/indexer functions.
• Engine::call_fn_dynamic for more control in calling script functions.

• Common operators (e.g. +, >, ==) now call into highly efficient built-in implementations for standard types (i.e. INT, FLOAT, bool, char, () and ImmutableString) if not overridden by a registered function. This yields a 5-10% speed benefit depending on script operator usage. Scripts running tight loops will see significant speed-up.
• Common assignment operators (e.g. +=, %=) now call into highly efficient built-in implementations for standard types (i.e. INT, FLOAT, bool, char, () and ImmutableString) if not overridden by a registered function.
• Implementations of common operators for standard types are removed from the ArithmeticPackage and LogicPackage (and therefore the CorePackage) because they are now always available, even under Engine::new_raw.
• Operator-assignment statements (e.g. +=) are now handled directly and much faster.
• Strings are now immutable and use the rhai::ImmutableString type, eliminating large amounts of cloning.
• For Native Rust functions taking a first &mut parameter, the first argument is passed by reference instead of by value, even if not called in method-call style. This allows many functions declared with &mut parameter to avoid excessive cloning. For example, if a is a large array, getting its length in this manner: len(a) used to result in a full clone of a before taking the length and throwing the copy away. Now, a is simply passed by reference, avoiding the cloning altogether.
• A custom hasher simply passes through u64 keys without hashing to avoid function call hash keys (which are by themselves u64) being hashed twice.

The major features for this release is modules, script resource limits, and speed improvements (mainly due to avoiding allocations).

• Modules and module resolvers allow loading external scripts under a module namespace. A module can contain constant variables, Rust functions and Rhai functions.
• export variables and private functions.
• Indexers for Rust types.
• Track script evaluation progress and terminate script run.
• Set limit on maximum number of operations allowed per script run.
• Set limit on maximum number of modules loaded per script run.
• A new API, Engine::compile_scripts_with_scope, can compile a list of script segments without needing to first concatenate them together into one large string.
• Stepped range function with a custom step.

A script contains many lists - statements in a block, arguments to a function call etc. In a typical script, most of these lists tend to be short - e.g. the vast majority of function calls contain fewer than 4 arguments, while most statement blocks have fewer than 4-5 statements, with one or two being the most common. Before, dynamic Vec's are used to hold these short lists for very brief periods of time, causing allocations churn.

In this version, large amounts of allocations are avoided by converting to a StaticVec - a list type based on a static array for a small number of items (currently four) - wherever possible plus other tricks. Most real-life scripts should see material speed increases.

Almost all variable lookups, as well as lookups in loaded modules, are now pre-computed. A variable's name is almost never used to search for the variable in the current scope.

Getters and setter function names are also pre-computed and cached, so no string allocations are performed during a property get/set call.

Lookup of all function calls, including Rust and Rhai ones, are now through pre-computed hashes. The function name is no longer used to search for a function, making function call dispatches much faster.

The expression (Expr) and statement (Stmt) types are modified so that all of the variants contain only one single Box to a large allocated structure containing all the fields. This makes the Expr and Stmt types very small (only one single pointer) and improves evaluation speed due to cache efficiency.

Previously, when an error occurs inside a function call, the error position reported is the function call site. This makes it difficult to diagnose the actual location of the error within the function.

A new error variant EvalAltResult::ErrorInFunctionCall is added in this version. It wraps the internal error returned by the called function, including the error position within the function.