Itertools

A library with utility functions and data types for creating efficient iterators in Motoko. This library is inspired by the itertools libraries in both python and rust.

Documentation

For a complete list of functions and data types, see the Itertools documentation

Demo: https://m7sm4-2iaaa-aaaab-qabra-cai.raw.ic0.app/?tag=1138180896

Getting started

To get started, you'll need to import the Iter module from both the base library and this one.

    import Iter "mo:base/Iter";
    import Itertools "mo:itertools/Iter";

Converting data types to iterators is the next step.

• Array

  • [1, 2, 3, 4, 5].vals()
  • Iter.fromArray([1, 2, 3, 4, 5])

• List

  • Iter.fromList(list)

• Text

  • "Hello, world!".chars()
  • Text.split("a,b,c", #char ',')

• Buffer

  • Buffer.toArray(buffer).vals()

For conversion of other data types to iterators, you can look in the base library for the specific data type's documentation.

Here are some examples of using the functions in this library to create simple and efficient iterators for solving different problems:

• An example, using range and sum to find the sum of values from 1 to 25:

    let range = Itertools.range(1, 25 + 1);
    let sum = Itertools.sum(range);

    assert sum == ?325;

• Splitting an array into chunks of size 3:

    let vals = [1, 2, 3, 4, 5, 6].vals();
    let chunks = Itertools.chunks(vals, 3);

    assert Iter.toArray(chunks) == [[1, 2, 3], [4, 5, 6]];

• Finding the difference between consecutive elements in an array:

    let vals = [5, 3, 3, 7, 8, 10].vals();
    
    let tuples = Itertools.slidingTuples(vals);
    // Iter.toArray(tuples) == [(5, 3), (3, 3), (3, 7), (7, 8), (8, 10)]
    
    let diff = func (x : (Int, Int)) : Int { x.1 - x.0 };
    let iter = Iter.map(tuples, diff);

    assert Iter.toArray(iter) == [-2, 0, 4, 1, 2];

• Reversing a list of integers and chunking them

    import Itertools "mo:itertools/Iter";
    import RevIter "mo:itertools/RevIter";

    let arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

    // create a Reversible Iterator from an array
    let iter = RevIter.fromArray(arr);

    // reverse iterator
    let rev_iter = iter.rev();

    // Reversible Iterator gets typecasted to an Iter type
    let chunks = Itertools.chunks(rev_iter, 3);

    assert Iter.toArray(chunks) == [
        [10, 9, 8], [7, 6, 5], [4, 3, 2], [1]
    ];

Contributing

Any contributions to this library are welcome. Ways you can contribute:

• Fix a bug or typo
• Improve the documentation
• Make a function more efficient
• Suggest a new function to add to the library

Tests

• Download and Install vessel
• Run make test

Modules and Functions

PeekableIter

Iter to PeekableIter	fromIter

RevIter (Reversible Iterators)

Main Methods	new, map, range, intRange,
Collection to RevIter	fromArray, fromVarArray, fromDeque
RevIter to Collection	toArray, toVarArray, toDeque

Iter

Augmenting	accumulate, add, countAll, enumerate, flatten, flattenArray, intersperse, mapEntries, mapWhile,runLength,pad, padWithFn, partitionInPlace, prepend, successor, uniqueCheck
Combining	interleave, interleaveLongest, merge, kmerge, zip, zip3, zipLongest
Combinatorics	combinations, cartesianProduct, permutations
Look ahead	peekable, spy
Grouping	chunks, chunksExact, groupBy, splitAt, tuples, triples, unzip,
Repeating	cycle, repeat,
Selecting	find, findIndex, findIndices, mapFilter, max, min, minmax, nth, nthOrDefault, skip, skipWhile, stepBy, take, takeWhile, unique
Sliding Window	slidingTuples, slidingTriples
Summarising	all, any, count, equal, fold, mapReduce, notEqual, isSorted, isSortedDesc, isPartitioned, isUnique, product, reduce, sum,
Collection to Iter	fromArraySlice, fromTrieSet
Iter to Collection	toBuffer, toDeque, toText, toTrieSet
Others	inspect, range, intRange, ref, sort, tee,