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@thi.ng/transducers

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Note

This is one of 199 standalone projects, maintained as part of the @thi.ng/umbrella monorepo and anti-framework.

🚀 Please help me to work full-time on these projects by sponsoring me on GitHub. Thank you! ❤️

About

Collection of ~170 lightweight, composable transducers, reducers, generators, iterators for functional data transformations.

This library provides altogether ~170 transducers, reducers, sequence generators (ES6 generators/iterators) and additional supporting functions for composing data transformation pipelines.

The overall concept and many of the core functions offered here are directly inspired by the original Clojure implementation by Rich Hickey, though the implementation does heavily differ (also in contrast to some other JS based implementations) and dozens of less common, but generally highly useful operators have been added. See full list below.

Furthermore, most transducers & reducers provided here accept an optional input iterable, which allows them to be used directly as transformers instead of having to wrap them in one of the execution functions (i.e. transduce()/transduceRight(), reduce()/reduceRight(), iterator(), run(), step()). If called this way, transducer functions will return a transforming ES6 iterator (generator) and reducing functions will return a reduced result of the given input iterable.

Status

STABLE - used in production

Search or submit any issues for this package

9.0.0 release

This release corrects a longstanding stylistic issue regarding the order of generic type args given to Reducer<A, B>, which now uses the swapped & more logical order (i.e. reduce from A to B) and is the same order of generic type args for Transducer and AsyncTransducer / AsyncReducer (in the thi.ng/transducers-async package). Most userland code should be unimpacted by this change - this is only a breaking change for custom reducer impls.

Support packages

Related packages

Blog posts

Installation

yarn add @thi.ng/transducers

ESM import:

import * as tx from "@thi.ng/transducers";

Browser ESM import:

<script type="module" src="https://esm.run/@thi.ng/transducers"></script>

JSDelivr documentation

For Node.js REPL:

const tx = await import("@thi.ng/transducers");

Package sizes (brotli'd, pre-treeshake): ESM: 9.05 KB

Dependencies

Note: @thi.ng/api is in most cases a type-only import (not used at runtime)

Usage examples

73 projects in this repo's /examples directory are using this package:

Screenshot Description Live demo Source
Interactive image processing (adaptive threshold) Demo Source
ASCII art raymarching with thi.ng/shader-ast & thi.ng/text-canvas Demo Source
Large ASCII font text generator using @thi.ng/rdom Demo Source
Figlet-style bitmap font creation with transducers Demo Source
Self-modifying, animated typographic grid with emergent complex patterns Demo Source
2D transducer based cellular automata Demo Source
Tool to interactively compute & visualize color contrasts against WCAG threshold Demo Source
Heatmap visualization of this mono-repo's commits Source
Filterable commit log UI w/ minimal server to provide commit history Demo Source
Basic crypto-currency candle chart with multiple moving averages plots Demo Source
Color palette generation via dominant color extraction from uploaded images Demo Source
Interactive visualization of closest points on ellipses Demo Source
Interactive inverse FFT toy synth Demo Source
Fiber-based cooperative multitasking basics Demo Source
Shape conversions & operations using polygons with holes Demo Source
Piechart visualization of CSV data Demo Source
Hex grid generation & tessellations Demo Source
GPU-based data reduction using thi.ng/shader-ast & WebGL multi-pass pipeline Demo Source
Visualization of different grid iterator strategies Demo Source
hdom update performance benchmark w/ config options Demo Source
Realtime analog clock demo Demo Source
Interactive pattern drawing demo using transducers Demo Source
Various hdom-canvas shape drawing examples & SVG conversion / export Demo Source
Custom dropdown UI component w/ fuzzy search Demo Source
Isolated, component-local DOM updates Demo Source
Basic hiccup-based canvas drawing Demo Source
Canvas based Immediate Mode GUI components Demo Source
Animated sine plasma effect visualized using contour lines Demo Source
Transforming JSON into UI components Demo Source
Randomized space-filling, nested grid layout generator Demo Source
Browser REPL for a Lispy S-expression based mini language Demo Source
Worker based, interactive Mandelbrot visualization Demo Source
Mastodon API feed reader with support for different media types, fullscreen media modal, HTML rewriting Demo Source
CLI util to visualize umbrella pkg stats Source
Parser grammar livecoding editor/playground & codegen Demo Source
RGB waveform image analysis Demo Source
Polygon to cubic curve conversion & visualization Demo Source
Animated, iterative polygon subdivisions & visualization Demo Source
Procedural stochastic text generation via custom DSL, parse grammar & AST transformation Demo Source
Unison wavetable synth with waveform editor Demo Source
Demonstates various rdom usage patterns Demo Source
Minimal rdom-canvas animation Demo Source
rstream & transducer-based FSM for converting key event sequences into high-level commands Demo Source
rdom & hiccup-canvas interop test Demo Source
Full umbrella repo doc string search w/ paginated results Demo Source
rdom powered SVG graph with draggable nodes Demo Source
Defining & using basic Web Components (with shadow DOM) via @thi.ng/rdom & @thi.ng/meta-css Demo Source
Responsive image gallery with tag-based Jaccard similarity ranking Demo Source
Generative audio synth offline renderer and WAV file export Demo Source
Animated Voronoi diagram, cubic splines & SVG download Demo Source
Minimal rstream dataflow graph Demo Source
Minimal demo of using rstream constructs to form an interceptor-style event loop Demo Source
Interactive grid generator, SVG generation & export, undo/redo support Demo Source
rstream based UI updates & state handling Demo Source
Minimal rstream sync() example using rdom Demo Source
2D scenegraph & shape picking Demo Source
Shader-AST meta-programming techniques for animated function plots Demo Source
Fork-join worker-based raymarch renderer (JS/CPU only) Demo Source
Simplistic SVG bar chart component Demo Source
SVG path parsing & dynamic resampling Demo Source
Additive waveform synthesis & SVG visualization with undo/redo Demo Source
hdom based slide deck viewer & slides from my ClojureX 2018 keynote Demo Source
Tree-based UI to find & explore thi.ng projects via their associated keywords Demo Source
Multi-layer vectorization & dithering of bitmap images Demo Source
Triple store query results & sortable table Demo Source
Interactive ridge-line plot Demo Source
rdom & WebGL-based image channel editor Demo Source
WebGL multi-colored cube mesh Demo Source
Drawing to floating point offscreen / multi-pass shader pipeline Demo Source
WebGL instancing, animated grid Demo Source
WebGL MSDF text rendering & particle system Demo Source
1D Wolfram automata with OBJ point cloud export Demo Source
XML/HTML/SVG to hiccup/JS conversion Demo Source

Basic usage patterns

import { comp, distinct, filter, map } from "@thi.ng/transducers";

// compose transducer
xform = comp(
    filter((x) => (x & 1) > 0), // odd numbers only
    distinct(),                 // distinct numbers only
    map((x) => x * 3)           // times 3
);

import { transduce, push } from "@thi.ng/transducers";

// collect into array (push)
transduce(xform, push(), [1, 2, 3, 4, 5, 4, 3, 2, 1]);
// [ 3, 9, 15 ]

// re-use same xform, but collect into ES6 Set
transduce(xform, conj(), [1, 2, 3, 4, 5, 4, 3, 2, 1]);
// Set { 3, 9, 15 }

import { iterator } from "@thi.ng/transducers";

// or apply as transforming iterator
// no reduction, only transformations
[...iterator(xform, [1, 2, 3, 4, 5])]
// [ 3, 9, 15]

// alternatively provide an input iterable and
// use xform as transforming iterator
[...filter((x) => /[A-Z]/.test(x), "Hello World!")]
// ["H", "W"]

import { step } from "@thi.ng/transducers";

// single step execution
// returns undefined if transducer returned no result for this input
// returns array if transducer step produced multiple results
f = step(xform);
f(1) // 3
f(2) // undefined
f(3) // 9
f(4) // undefined

f = step(take)

Interpolation & SVG generation

This example uses the @thi.ng/geom package for quick SVG generation.

example output

import { asSvg, svgDoc, circle, polyline } from "@thi.ng/geom";

// source values
const values = [5, 10, 4, 8, 20, 2, 11, 7];

// interpolate values and transform into 2D points
const vertices = [...iterator(
    comp(
        interpolateHermite(10),
        mapIndexed((x, y) => [x, y])
    ),
    // duplicate first & last vals (1x LHS / 2x RHS)
    // this is only needed for hermite interpolation
    // (see doc string for `interpolateHermite`)
    extendSides(values, 1, 2)
)];

// generate SVG
asSvg(
    svgDoc(
        { width: 800, height: 200, "stroke-width": 0.1 },
        // interpolated points as polyline
        polyline(vertices, { stroke: "red" }),
        // original values as dots
        ...values.map((y, x) => circle([x * 10, y], 0.2))
    )
)

Fuzzy search

import { filterFuzzy } from "@thi.ng/transducers";

[...filterFuzzy("ho", ["hello", "hallo", "hey", "heyoka"])]
// ["hello", "hallo", "heyoka"]
[...filterFuzzy("hlo", ["hello", "hallo", "hey", "heyoka"])]
// ["hello", "hallo"]

// works with any array-like values & supports custom key extractors
[...filterFuzzy(
    [1, 3],
    { key: (x) => x.tags },
    [
        { tags: [1, 2, 3] },
        { tags: [2, 3, 4] },
        { tags: [4, 5, 6] },
        { tags: [1, 3, 6] }
    ]
)]
// [ { tags: [ 1, 2, 3 ] }, { tags: [ 1, 3, 6 ] } ]

Histogram generation & result grouping

import { frequencies, map, reduce, transduce } from "@thi.ng/transducers";

// use the `frequencies` reducer to create
// a map counting occurrence of each value
transduce(map((x) => x.toUpperCase()), frequencies(), "hello world");
// Map { 'H' => 1, 'E' => 1, 'L' => 3, 'O' => 2, ' ' => 1, 'W' => 1, 'R' => 1, 'D' => 1 }

// reduction only (no transform)
reduce(frequencies(), [1, 1, 1, 2, 3, 4, 4]);
// Map { 1 => 3, 2 => 1, 3 => 1, 4 => 2 }

// direct reduction if input is given
frequencies([1, 1, 1, 2, 3, 4, 4]);
// Map { 1 => 3, 2 => 1, 3 => 1, 4 => 2 }

// with optional key function, here to bin by word length
frequencies(
    (x) => x.length,
    "my camel is collapsing and needs some water".split(" ")
);
// Map { 2 => 2, 5 => 3, 10 => 1, 3 => 1, 4 => 1 }
import { groupByMap } from "@thi.ng/transducers";

// actual grouping (here: by word length)
groupByMap(
    { key: (x) => x.length },
    "my camel is collapsing and needs some water".split(" ")
);
// Map {
//   2 => [ 'my', 'is' ],
//   3 => [ 'and' ],
//   4 => [ 'some' ],
//   5 => [ 'camel', 'needs', 'water' ],
//   10 => [ 'collapsing' ]
// }

Pagination

import { page, comp, iterator, map, padLast, range } from "@thi.ng/transducers";

// extract only items for given page id & page length
[...page(0, 5, range(12))]
// [ 0, 1, 2, 3, 4 ]

// when composing with other transducers
// it's most efficient to place `page()` early on in the chain
// that way only the page items will be further processed
[...iterator(comp(page(1, 5), map(x => x * 10)), range(12))]
// [ 50, 60, 70, 80, 90 ]

// use `padLast()` to fill up missing values
[...iterator(comp(page(2, 5), padLast(5, "n/a")), range(12))]
// [ 10, 11, 'n/a', 'n/a', 'n/a' ]

// no values produced for invalid pages
[...page(3, 5, range(12))]
// []

Multiplexing / parallel transducer application

multiplex and multiplexObj can be used to transform values in parallel using the provided transducers (which can be composed as usual) and results in a tuple or keyed object.

import { map, multiplex, multiplexObj, push, transduce } from "@thi.ng/transducers";

transduce(
    multiplex(
        map((x) => x.charAt(0)),
        map((x) => x.toUpperCase()),
        map((x) => x.length)
    ),
    push(),
    ["Alice", "Bob", "Charlie"]
);
// [ [ "A", "ALICE", 5 ], [ "B", "BOB", 3 ], [ "C", "CHARLIE", 7 ] ]

transduce(
    multiplexObj({
        initial: map((x) => x.charAt(0)),
        name: map((x) => x.toUpperCase()),
        len: map((x) => x.length)
    }),
    push(),
    ["Alice", "Bob", "Charlie"]
);
// [ { len: 5, name: 'ALICE', initial: 'A' },
//   { len: 3, name: 'BOB', initial: 'B' },
//   { len: 7, name: 'CHARLIE', initial: 'C' } ]

Moving average using sliding window

import { comp, map, mean, partition, push, reduce transduce } from "@thi.ng/transducers";

// use nested reduce to compute window averages
transduce(
    comp(
        partition(5, 1),
        map(x => reduce(mean(), x))
    ),
    push(),
    [1, 2, 3, 3, 4, 5, 5, 6, 7, 8, 8, 9, 10]
)
// [ 2.6, 3.4, 4, 4.6, 5.4, 6.2, 6.8, 7.6, 8.4 ]

This combined transducer is also directly available as:

import { movingAverage } from "@thi.ng/transducers";

[...movingAverage(5, [1, 2, 3, 3, 4, 5, 5, 6, 7, 8, 8, 9, 10])]
// [ 2.6, 3.4, 4, 4.6, 5.4, 6.2, 6.8, 7.6, 8.4 ]

Benchmark function execution time

import { benchmark, mean, repeatedly, transduce } from "@thi.ng/transducers";

// function to test
fn = () => {
    let x;
    for (i = 0; i < 1e6; i++) {
        x = Math.cos(i);
    }
    return x;
};

// compute the mean of 100 runs
transduce(benchmark(), mean(), repeatedly(fn, 100));
// 1.93 (milliseconds)

Apply inspectors to debug transducer pipeline

import { comp, filter, map, push, trace, transduce } from "@thi.ng/transducers";

// alternatively, use sideEffect() for arbitrary side fx
transduce(
    comp(
        trace("orig"),
        map((x) => x + 1),
        trace("mapped"),
        filter((x) => (x & 1) > 0)
    ),
    push(),
    [1, 2, 3, 4]
);
// orig 1
// mapped 2
// orig 2
// mapped 3
// orig 3
// mapped 4
// orig 4
// mapped 5
// [ 3, 5 ]

Stream parsing / structuring

The struct transducer is simply a composition of: partitionOf -> partition -> rename -> mapKeys. See code here.

import { struct } from "@thi.ng/transducers";

// Higher-order transducer to convert linear input into structured objects
// using given field specs and ordering. A single field spec is an array of
// 2 or 3 items: `[name, size, transform?]`. If `transform` is given, it will
// be used to produce the final value for this field. In the example below,
// it is used to unwrap the ID field values, e.g. from `[0] => 0`
[
    ...struct(
        [["id", 1, (id) => id[0]], ["pos", 2], ["vel", 2], ["color", 4]],
        [0, 100, 200, -1, 0, 1, 0.5, 0, 1, 1, 0, 0, 5, 4, 0, 0, 1, 1]
    )
];
// [ { color: [ 1, 0.5, 0, 1 ],
//     vel: [ -1, 0 ],
//     pos: [ 100, 200 ],
//     id: 0 },
//   { color: [ 0, 0, 1, 1 ],
//     vel: [ 5, 4 ],
//     pos: [ 0, 0 ],
//     id: 1 } ]

CSV parsing

import { comp, map, mapcat, push, rename, transduce } from "@thi.ng/transducers";

transduce(
    comp(
        // split into rows
        mapcat((x) => x.split("\n")),
        // split each row
        map((x) => x.split(",")),
        // convert each row into object, rename array indices
        rename({ id: 0, name: 1, alias: 2, num: "length" })
    ),
    push(),
    ["100,typescript\n101,clojure,clj\n110,rust,rs"]
);
// [ { num: 2, name: 'typescript', id: '100' },
//   { num: 3, alias: 'clj', name: 'clojure', id: '101' },
//   { num: 3, alias: 'rs', name: 'rust', id: '110' } ]

Early termination

import { comp, flatten, push, take, transduce } from "@thi.ng/transducers";

// result is realized after max. 7 values, irrespective of nesting
transduce(comp(flatten(), take(7)), push(), [
    1,
    [2, [3, 4, [5, 6, [7, 8], 9, [10]]]]
]);
// [1, 2, 3, 4, 5, 6, 7]

Scan operator

import {
    comp, count, iterator, map, push, pushCopy, repeat, scan, transduce
} from "@thi.ng/transducers";

// this transducer uses 2 scans (a scan = inner reducer per item)
// 1) counts incoming values
// 2) forms an array of the current counter value `x` & repeated `x` times
// 3) emits results as series of reductions in the outer array produced
//    by the main reducer
// IMPORTANT: since arrays are mutable we use `pushCopy` as the inner reducer
// instead of `push` (the outer reducer)
xform = comp(
    scan(count()),
    map(x => [...repeat(x,x)]),
    scan(pushCopy())
)

[...iterator(xform, [1, 1, 1, 1])]
// [ [ [ 1 ] ],
//   [ [ 1 ], [ 2, 2 ] ],
//   [ [ 1 ], [ 2, 2 ], [ 3, 3, 3 ] ],
//   [ [ 1 ], [ 2, 2 ], [ 3, 3, 3 ], [ 4, 4, 4, 4 ] ] ]

// more simple & similar to previous, but without the 2nd xform step
transduce(comp(scan(count()), scan(pushCopy())), push(), [1,1,1,1])
// [ [ 1 ], [ 1, 2 ], [ 1, 2, 3 ], [ 1, 2, 3, 4 ] ]

Weighted random choices

import { choices, frequencies, take, transduce } from "@thi.ng/transducers";

[...take(10, choices("abcd", [1, 0.5, 0.25, 0.125]))]
// [ 'a', 'a', 'b', 'a', 'a', 'b', 'a', 'c', 'd', 'b' ]

transduce(
    take(1000),
    frequencies(),
    choices("abcd", [1, 0.5, 0.25, 0.125])
);
// Map { 'c' => 132, 'a' => 545, 'b' => 251, 'd' => 72 }

Keyframe interpolation

See tween() docs for details.

import { tween } from "@thi.ng/transducers";

[
    ...tween(
        10,
        0,
        100,
        (a, b) => [a, b],
        ([a, b], t) => Math.floor(a + (b - a) * t),
        [20, 100],
        [50, 200],
        [80, 0]
    )
];
// [ 100, 100, 100, 133, 166, 200, 133, 66, 0, 0, 0 ]

API

Generated API docs

Types

Apart from type aliases, the only real types defined are:

Reducer

Reducers are the core building blocks of transducers. Unlike other implementations using OOP approaches, a Reducer in this lib is a simple 3-element array of functions, each addressing a separate processing step.

The bundled reducers are all wrapped in functions to provide a uniform API (and some of them can be preconfigured and/or are stateful closures). However, it's completely fine to define stateless reducers as constant arrays.

A Reducer is a 3-tuple of functions defining the different stages of a reduction process: A Reducer<A, B> reduces values of type A to a single value of type B.

The tuple items/functions in order:

  1. Initialization function used to produce an initial default result (only used if no such initial result was given by the user)
  2. Completion function to post-process an already reduced result (for most reducers this is merely the identity function)
  3. Accumulation function, merging a new input value with the currently existing (partially) reduced result/accumulator
type Reducer<A, B> = [
    // init
    () => B,
    // completion
    (x: B) => B,
    // accumulation
    (acc: B, x: A) => B
];

// A concrete example:
const push: Reducer<any, any[]> = [
    // init
    () => [],
    // completion (nothing to do in this case)
    (acc) => acc,
    // accumulation
    (acc, x) => (acc.push(x), acc)
];

Reduced

Simple type wrapper to mark & identify a reducer's early termination. Does not modify wrapped value by injecting magic properties.

import type { IDeref } from "@thi.ng/api";

class Reduced<T> implements IDeref<T> {
    protected value: T;
    constructor(val: T);
    deref(): T;
}

Instances can be created via reduced(x) and handled via these helper functions:

  • reduced(x: any): any
  • isReduced(x: any): boolean
  • ensureReduced(x: any): Reduced<any>
  • unreduced(x: any): any

IReducible

By default reduce() consumes inputs via the standard ES6 Iterable interface, i.e. using a for..of.. loop, but the function also supports optimized routes for some types: Array-like inputs are consumed via a traditional for-loop and custom optimized iterations can be provided via implementations of the IReducible interface in the source collection type. Examples can be found here:

Note: The IReducible interface is only used by reduce(), transduce() and run().

Transducer

From Rich Hickey's original definition:

A transducer is a transformation from one reducing function to another

As shown in the examples above, transducers can be dynamically composed (using comp()) to form arbitrary data transformation pipelines without causing large overheads for intermediate collections.

type Transducer<A, B> = (rfn: Reducer<B, any>) => Reducer<A, any>;

// concrete example of a stateless transducer (expanded for clarity)
function map<A, B>(fn: (x: A) => B): Transducer<A, B> {
    return ([init, complete, reduce]: Reducer<B, any>) => {
        return <Reducer<A, any>>[
            init,
            complete,
            (acc, x: A) => reduce(acc, fn(x))
        ];
    };
}

// stateful transducer
// removes successive value repetitions
function dedupe<T>(): Transducer<T, T> {
    return ([init, complete, reduce]: Reducer<T, any>) => {
        // state initialization
        let prev = {};
        return <Reducer<T, any>>[
            init,
            complete,
            (acc, x) => {
                if (prev !== x) acc = reduce(acc, x);
                prev = x;
                return acc;
            }
        ];
    };
}

IXform interface

Interface for types able to provide some internal functionality (or derive some related transformation) as Transducer. Implementations of this interface can be directly passed to all functions in this package where a Transducer arg is expected.

import { map, push, range, transduce, type IXform } from "@thi.ng/transducers";

class Mul implements IXform<number, number> {

    constructor(public factor = 10) {}

    xform() {
        return map((x) => this.factor * x);
    }
}

transduce(new Mul(11), push(), range(4))
// [0, 11, 22, 33, 44]

import { comp, drop, push, range, takeNth, transduce } from "@thi.ng/transducers";

// also usable w/ comp(), iterator(), step(), run() etc.
transduce(
    comp(drop(1), new Mul(11), takeNth(2)),
    push(),
    range(4)
)
// [11, 33]

Composition & execution

comp

comp(f1, f2, ...)

Returns new transducer composed from given transducers. Data flow is from left to right. Offers fast paths for up to 10 args. If more are given, composition is done dynamically via for loop.

compR

compR(rfn: Reducer<any, any>, fn: (acc, x) => any): Reducer<any, any>

Helper function to compose reducers.

iterator

iterator<A, B>(tx: Transducer<A, B>, xs: Iterable<A>): IterableIterator<B>

Similar to transduce(), but emits results as ES6 iterator (and hence doesn't use a reduction function).

reduce

reduce<A, B>(rfn: Reducer<A, B>, acc?: A, xs: Iterable<B>): A

Reduces xs using given reducer and optional initial accumulator/result. If xs implements the IReducible interface, delegates to that implementation. Likewise, uses a fast route if xs is an ArrayLike type.

reduceRight

reduceRight<A, B>(rfn: Reducer<A, B>, acc?: A, xs: ArrayLike<B>): A

Similar to reduce, however only accepts ArrayLike sources and reduces them into right-to-left order.

transduce

transduce<A, B, C>(tx: Transducer<A, B>, rfn: Reducer<C, B>, acc?: C, xs: Iterable<A>): C

Transforms iterable using given transducer and combines results with given reducer and optional initial accumulator/result.

transduceRight

transduceRight<A, B, C>(tx: Transducer<A, B>, rfn: Reducer<C, B>, acc?: C, xs: ArrayLike<A>): C

Similar to transduce, however only accepts ArrayLike sources and processes them into right-to-left order.

run

run<A, B>(tx: Transducer<A, B>, fx: (x: B) => void, xs: Iterable<A>)

Transforms iterable with given transducer and optional side effect without any reduction step. If fx is given it will be called with every value produced by the transducer. If fx is not given, the transducer is assumed to include at least one sideEffect() step itself. Returns nothing.

consume

consume(src: Iterable<any>): void

Similar to run(), consumes given iterable, presumably for any implicit side-effects. Iterable MUST be finite!

import { consume, repeatedly2d } from "@thi.ng/transducers";

// here the function given to repeatedly2d() has only a side-effect, however
// repeatedly2d() itself is lazy. Using consume() then forces this lazy iterator/generator
// to be realized and so also the side-effects to be executed
consume(repeatedly2d((x, y) => console.log("output:", [x, y]), 2, 3));
// output: [ 0, 0 ]
// output: [ 1, 0 ]
// output: [ 0, 1 ]
// output: [ 1, 1 ]
// output: [ 0, 2 ]
// output: [ 1, 2 ]

Transducers

All of the following functions can be used and composed as transducers. With a few exceptions, most also accept an input iterable and then directly yield a transforming iterator, e.g.

import { map, push, range, transduce } from "@thi.ng/transducers";

// as transducer
transduce(map((x) => x*10), push(), range(4))
// [ 0, 10, 20, 30 ]

// as transforming iterator
[...map((x) => x*10, range(4))]
// [ 0, 10, 20, 30 ]

Generators / Iterators

Reducers

As with transducer functions, reducer functions can also given an optional input iterable. If done so, the function will consume the input and return a reduced result (as if it would be called via reduce()).

Authors

If this project contributes to an academic publication, please cite it as:

@misc{thing-transducers,
  title = "@thi.ng/transducers",
  author = "Karsten Schmidt and others",
  note = "https://thi.ng/transducers",
  year = 2016
}

License

© 2016 - 2024 Karsten Schmidt // Apache License 2.0