Lazy evaluated iterators in Solidity.
We wrap a uint256 memory array and enable up to 15 different functions to map over each element.
Note that due to laziness, calling .map does not loop over the iterator immediately.
The iterator may only advance by one with the .next method and by the remainder of the iterator
with the .collect method.
forge install jtriley-eth/iter-solimport {Iter, toIter} from "lib/iter-sol/src/Lib.sol";
using { toIter } for uint256[];
// -- snip --
function addOneDoubleThenSubOne(uint256[] meomry arr) pure returns (uint256[] memory) {
return arr.toIter()
.map(addOne)
.map(double)
.map(subOne)
.collect();
}
// -- utilities --
function double(uint256 x) pure returns (uint256) {
return x * 2;
}
function addOne(uint256 x) pure returns (uint256) {
return x + 1;
}
function subOne(uint256 x) pure returns (uint256) {
return x - 1;
}Main iterator structure, wraps the array.
Converts a uint256[] into an Iter.
Advances the iterator by one, applying all mapped functions over the element.
Note: returns zero if empty
Advances the iterator to the end of the inner array, applying all mapped functions over each element
and collecting the result into a uint256[].
Maps a single internal function over the iterator.
Internal function signature must be as follows.
function(uint256) pure returns (uint256)Converts the function to a generalized Fn type.
Converts the Fn type to uint256
Gets the length of the dispatcher. This is not the number of elements in the iterator, rather it is the number of functions to map over.
Appends another function to the dispatcher. This is not necessary to access from the outside, this
is for the Iter.map method.
Loops each function and calls each against a single element.