@thi.ng/transducers

@thi.ng/transducers

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[!NOTE] This is one of 190 standalone projects, maintained as part of the @thi.ng/umbrella monorepo and anti-framework.

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About

Lightweight transducer implementations for ES6 / TypeScript.

This library provides altogether ~130 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

7.0.0 release

Thanks to a PR and related issue by @gavinpc-mindgrub, various transducers functions have been fixed for the case when they're invoked with an empty string as input iterable. Furthermore, flatten() is always treating strings as atomic values now, whereas before top-level strings would be split into individual characters.

6.0.0 release

BREAKING CHANGES:

  • The interpolate iterator for keyframe interpolation has been renamed to tween. In its place there's a new higher order transducer called interpolate, incl. syntax-sugar versions interpolateHermite and interpolateLinear.
  • The previously deprecated wrapLeft, wrapRight and wrapBoth iterators have been removed.
  • The wrap iterator has been renamed to wrapSides and has a new signature/arguments, more aligned with the ones listed below.

The following new iterators have been added:

  • extendSides
  • padSides
  • symmetric

5.0.0 release

Several previously included internal support functions have been migrated to the @thi.ng/arrays package. You'll need to update your imports if you've been using any of these directly. Note that some of these functions also have changes to their arg order. See changelog.

Functions using randomness now all support an optional PRNG implementation of the IRandom interface from the @thi.ng/random package.

Support packages

Related packages

Blog posts

Installation

yarn add @thi.ng/transducers

ES module import:

<script type="module" src="https://cdn.skypack.dev/@thi.ng/transducers"></script>

Skypack documentation

For Node.js REPL:

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

Package sizes (brotli'd, pre-treeshake): ESM: 8.89 KB

Dependencies

Usage examples

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

ScreenshotDescriptionLive demoSource
Interactive image processing (adaptive threshold)DemoSource
ASCII art raymarching with thi.ng/shader-ast & thi.ng/text-canvasDemoSource
Large ASCII font text generator using @thi.ng/rdomDemoSource
Figlet-style bitmap font creation with transducersDemoSource
Self-modifying, animated typographic grid with emergent complex patternsDemoSource
2D transducer based cellular automataDemoSource
Heatmap visualization of this mono-repo's commitsSource
Filterable commit log UI w/ minimal server to provide commit historyDemoSource
Basic crypto-currency candle chart with multiple moving averages plotsDemoSource
Color palette generation via dominant color extraction from uploaded imagesDemoSource
Interactive visualization of closest points on ellipsesDemoSource
Interactive inverse FFT toy synthDemoSource
Fiber-based cooperative multitasking basicsDemoSource
Visualization of different grid iterator strategiesDemoSource
hdom update performance benchmark w/ config optionsDemoSource
Realtime analog clock demoDemoSource
Interactive pattern drawing demo using transducersDemoSource
Various hdom-canvas shape drawing examples & SVG conversion / exportDemoSource
Custom dropdown UI component w/ fuzzy searchDemoSource
Isolated, component-local DOM updatesDemoSource
Basic hiccup-based canvas drawingDemoSource
Canvas based Immediate Mode GUI componentsDemoSource
Animated sine plasma effect visualized using contour linesDemoSource
Transforming JSON into UI componentsDemoSource
Randomized space-filling, nested grid layout generatorDemoSource
Browser REPL for a Lispy S-expression based mini languageDemoSource
Worker based, interactive Mandelbrot visualizationDemoSource
Mastodon API feed reader with support for different media types, fullscreen media modal, HTML rewritingDemoSource
CLI util to visualize umbrella pkg statsSource
Parser grammar livecoding editor/playground & codegenDemoSource
RGB waveform image analysisDemoSource
Polygon to cubic curve conversion & visualizationDemoSource
Animated, iterative polygon subdivisions & visualizationDemoSource
Procedural stochastic text generation via custom DSL, parse grammar & AST transformationDemoSource
Unison wavetable synth with waveform editorDemoSource
Demonstates various rdom usage patternsDemoSource
Minimal rdom-canvas animationDemoSource
rstream & transducer-based FSM for converting key event sequences into high-level commandsDemoSource
rdom & hiccup-canvas interop testDemoSource
Full umbrella repo doc string search w/ paginated resultsDemoSource
rdom powered SVG graph with draggable nodesDemoSource
Responsive image gallery with tag-based Jaccard similarity rankingDemoSource
Generative audio synth offline renderer and WAV file exportDemoSource
Animated Voronoi diagram, cubic splines & SVG downloadDemoSource
Minimal rstream dataflow graphDemoSource
Minimal demo of using rstream constructs to form an interceptor-style event loopDemoSource
Interactive grid generator, SVG generation & export, undo/redo supportDemoSource
rstream based UI updates & state handlingDemoSource
Minimal rstream sync() example using rdomDemoSource
2D scenegraph & shape pickingDemoSource
Shader-AST meta-programming techniques for animated function plotsDemoSource
Fork-join worker-based raymarch renderer (JS/CPU only)DemoSource
Simplistic SVG bar chart componentDemoSource
SVG path parsing & dynamic resamplingDemoSource
Additive waveform synthesis & SVG visualization with undo/redoDemoSource
hdom based slide deck viewer & slides from my ClojureX 2018 keynoteDemoSource
Multi-layer vectorization & dithering of bitmap imagesDemoSource
Triple store query results & sortable tableDemoSource
rdom & WebGL-based image channel editorDemoSource
WebGL multi-colored cube meshDemoSource
Drawing to floating point offscreen / multi-pass shader pipelineDemoSource
WebGL instancing, animated gridDemoSource
WebGL MSDF text rendering & particle systemDemoSource
1D Wolfram automata with OBJ point cloud exportDemoSource
XML/HTML/SVG to hiccup/JS conversionDemoSource

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.

Since v0.6.0 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 fine to define stateless reducers as constant arrays.

interface Reducer<A, B> extends Array<any> {
/**
* Initialization, e.g. to provide a suitable accumulator value,
* only called when no initial accumulator has been provided by user.
*/
[0]: () => A;
/**
* Completion. When called usually just returns `acc`, but stateful
* transformers should flush/apply their outstanding results.
*/
[1]: (acc: A) => A;
/**
* Reduction step. Combines new input with accumulator.
* If reduction should terminate early, wrap result via `reduced()`
*/
[2]: (acc: A, x: B) => A | Reduced<A>;
}

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

partition, partitionBy, streamSort, streamShuffle are (examples of) transducers making use of their 1-arity completing function.

Reduced

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

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

Simple type wrapper to identify early termination of a reducer. Does not modify wrapped value by injecting magic properties. 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 uses 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<any, B>) => Reducer<any, A>;

// concrete example of stateless transducer (expanded for clarity)
function map<A, B>(fn: (x: A) => B): Transducer<A, B> {
return (rfn: Reducer<any, B>) => {
return [
() => rfn[0](),
(acc) => rfn[1](acc),
(acc, x: A) => rfn[2](acc, fn(x))
];
};
}

// stateful transducer
// removes successive value repetitions
function dedupe<T>(): Transducer<T, T> {
return (rfn: Reducer<any, T>) => {
// state initialization
let prev = {};
return [
() => rfn[0](),
(acc) => rfn[1](acc),
(acc, x) => {
acc = prev === x ? acc : rfn[2](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

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