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  • Jan 31 2019 22:17
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    CrossEye commented #2777
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    mbostock commented #2772
  • Jan 29 2019 15:48
    CrossEye commented #2772
In all honesty mate it does all the hard work, I'd highly recommend it
woss ( Daniel Maricic )
on this link there is plenty of ramda code for recursive execution and loading. although this works only on node but YES now i can do it in browser https://github.com/anagolay/js-sdk/blob/main/sdk/core/src/executeOperation.ts#L42
Nice. I'm loving some of the comments in that repo :joy:
Charles Hughes
kind of proud of this little tool I made last night:
const tagger = curry((tag, text, template) => pipe(
      replace(tag, text),
      tagger(tag, text)

const applyTags = (tags, template) =>
    map(over(lensIndex(0), s => `{${s}}`)),
    reduce(pipe(append, apply(tagger)), template)

const tags = {
  test: 'tasty test',
  cheese: 'amazing smoked gouda'
const template = 'this is a {test}. I love {cheese}.'

applyTags(tags, template) // "this is a tasty test. I love amazing smoked gouda."
4 replies
stupid question. includes is T => T[] => boolean. Is there an equivalent function in ramda that is T[] => T => boolean?
i just add my own:
const includedIn: <T>(list: T[]) => (item: T) => boolean =
    list => item => includes(item)(list)
i just want to make sure that i'm not doing something that ramda already supports that i just cant find in the docs XD
1 reply
Mike Vosseller

Hi, I'm new to functional programming and Ramda. How might you improve these functions? Can any be made pointfree? Thank you!

// elementAfter(el, list) returns the element after el in the list
// (wapping to the beginning if needed)
// how would you improve these functions? can any be made pointfree?
const indexAfter = (index, list) => mathMod(inc(index), length(list))
const indexAfterElement = (el, list) => indexAfter(indexOf(el, list), list)
const elementAfter = (el, list) => nth(indexAfterElement(el, list), list)
elementAfter('c', ['a', 'b', 'c']) // 'a'

Ramda REPL: https://tinyurl.com/yhwpgykj

11 replies
Joshua Travis
Hi! I'm wanting to use a transducer to do a filter, map on a data set and then join then via effectively a groupBy. While I can write my own joiner, I'd like to know if there's a way that I can use the Ramda groupBy instead.
// This fails cause "reduce: list must be array or iterable"
R.transduce(mapfilterComp, R.groupBy(R.prop('programId')), {}, settings)
4 replies
@mpv_twitter I could improve indexAfter
@mpv_twitter I could do it even more with reader monad
I made it point free with the help of pointfree.io
I made it 100% point free but I couldn't read it lol
i just noticed someone solved it, also there is reader monad in ramda
Mike Vosseller
@theqp Thank you!
Andy Mac

// This is a function that returns a function with it's arguments re-arranged.
// I'm not sure how useful it is, i just wanted to make one.

// You specify the new argument order with an integer, with each digit from 1-9 
// symbolising the original order.

// for example, to switch the order of a binary function like divide, we use 21
// we're counting from 1.

// swap(21, divide)(4,2) //--> 0.5

// More complex now

// swap(42133, foo)(these, are, some, args, wow) 
// equiv. to:  foo(args, are, these, some, some)

// Note you can repeat numbers to pass to the same value multiple times.  
// The function applies curryN to the result based on how many digits there are, 
// giving you partial application, of sorts.

const swap = curry((n, f) => {
  const argMap = Array.from(n.toString()).map(x => parseInt(x) - 1)
  return curryN(argMap.length, (...args) =>
      ...addIndex(map)((a, i) => {
        const newPos = argMap.indexOf(i)
        return newPos !== -1 ? args[newPos] : a
      }, args)

Hi, I have the following code that is returning true when it should return false:

const isNotEmpty = R.complement(R.isEmpty)
const isNotNil = R.complement(R.isNil)

const isNotEmptyFeed = R.and(R.pathSatisfies(isNotEmpty, ['data', 'children']), isNotNil)

  subreddit: 'abruptchaos',
  feedCategory: 'posts_Default',
  feedUrl: 'https://www.reddit.com/r/abruptchaos/.json?limit=100&count=100&after=null',
  data: { children: [] },

Can anyone tell me where I've gone wrong here? data.children is empty, so that should be false right?

Andy Mac
@CoopCoding_twitter Try both instead of and
Thanks, that works.
Andy Mac
When you're having trouble like this, check the function signature in the docs to make sure the types match up.
Akira Cai

Hi there, does the following combinator have a name? Or, on the other hand, how we usually deal this pattern instead of composing with the combinator? For example:

// ???
const combinator = R.curry((f, g, x, y) => f (  g(x)  )  (  y  )  )

// findById :: ((Record K V -> Boolean) -> [Record K V] -> Maybe Record K V) -> (V -> Record K V -> Boolean) -> V -> [Record K V] -> Maybe Record K V
const findById = combinator(R.find, R.propEq("id"))

findById(1)([{id: 1}])
//> {id: 1}

I know the combinator can be derived from the following 2 functions, where g is identity.

But, is there a more elegant way to deal with it? Any suggestions or perspectives are welcome.

Andy Mac
Akira Cai

@zxol Thank you, it is exactly the same beta-reduction as mine. And then my following question comes up:
If the function is variadic, then I need a I** combinator to achieve the same functionality, does it make sense?

const idstarstar = R.curry((f, x, y) => f(x)(y))

// right associative
// findById :: (Pred -> [a] -> Maybe a) -> (v -> Pred) -> v -> ([a] -> Maybe a)
const findById = R.compose(R.find, R.propEq("id"))

idstarstar(findById)(1, [{id: 1}])

I think the problem is that f(g(x)) returns another function, so I can not give 2 arguments at once and apply to v -> ([a] -> Maybe a).
Is there a more elegant way to deal with it? Any suggestions or perspectives are welcome.

Andy Mac
@blackwindforce i don't know of any combinator in the ramda lib, unfortunately. Perhaps the best thing to do is try to structure your program's API so the functor you're operating on is always at the end of a function call on it's own like you used in the first example. Or do the useWith identity trick. Perhaps someone else has a neat answer for you
Akira Cai
@zxol Thank you, that make sense to me.
Mike Vosseller

Hi, I'm creating a simple tic-tac-toe style game and game state is stored in a game object.

I've noticed two problems:
1- most of my functions need access to the game object so I need to repeatedly pass it down.
2- because of #1 when I try to compose with a pipeline I often need to curry some functions with the game object.

Both seem like code smells. Is this typical? Any advice to improve?

(This code uses folktale Result)

import {
} from "ramda";
import folktale from "folktale";
const { result: Result } = folktale;

const createGame = ({ width, height } = {}) => ({
  size: {
  grid: Array(width * height), // game is a grid but stored as a flat array
  // additional game state goes here

// 1) most of my functions need access to the game object so I'm repeatedly passing it down. is this typical?
const gridIndex = (game, pos) => add(pos[0], multiply(pos[1], game.size.width));
const cell = (game, pos) => game.grid[gridIndex(game, pos)];
const updateCell = (game, pos, val) =>
    grid: (g) => update(gridIndex(game, pos), val, g),

// two contrived validators that don't require the game object
const validateColGte0 = (pos) =>
  pos[0] >= 0 ? Result.Ok(pos) : Result.Error(`col must be >= 0: ${pos[0]}`);
const validateRowGte0 = (pos) =>
  pos[1] >= 0 ? Result.Ok(pos) : Result.Error(`row must be >= 0: ${pos[1]}`);
// three validators that need the game object
const validateColLtWidth = curry((game, pos) =>
  pos[0] < game.size.width
    ? Result.Ok(pos)
    : Result.Error(`col must be < ${game.size.width}: ${pos[0]}`)
const validateRowLtHeight = curry((game, pos) =>
  pos[1] < game.size.height
    ? Result.Ok(pos)
    : Result.Error(`row must be < ${game.size.height}: ${pos[1]}`)
const validateCellIsEmpty = curry((game, pos) =>
  !cell(game, pos)
    ? Result.Ok(pos)
    : Result.Error(`position is not empty: ${pos}`)
// 2) To compose functions in a pipline I need to curry them with the game object
//    would it be better to make the validator signatures take a single object 
//    with all possible paramaters? e.g. { game, pos }
const validatePosition = (game, pos) =>
const performMove = (game, pos, val) =>
  validatePosition(game, pos).matchWith({
    Ok: ({ value: validatedPosition }) =>
      updateCell(game, validatedPosition, val),
    Error: ({ value: error }) => {
      return game;

// create and run the game
let game = createGame({ width: 3, height: 3 });
game = performMove(game, [1, 1], "X"); // works
game = performMove(game, [1, 1], "O"); // position is not empty: 1,1
6 replies
Charles Hughes
Is there a more elegant way to do this?
compose(join(''), converge(Array, [getDateTitle, always('\n\n'), getBodyWithoutMarkup])
4 replies
any developer for @types/ramda here?
1 reply
I have made a more accurate cond type definition but I don't want to download the whole @types repo
export function cond<A, B>(fns: Array<[SafePred<A>, (...a: readonly A[]) => B]>): (...a: readonly A[]) => B | undefined;
export function cond<A, B>(
    fns: [
      ...[SafePred<A>, (...a: readonly A[]) => B],
      [(...a: readonly A[]) => true, (...a: readonly A[]) => B],
      ...[SafePred<A>, (...a: readonly A[]) => B]
  ): (...a: readonly A[]) => B;
also the one with any makes no sense to me, B can be any
Mike Vosseller

Looks like Ramda doesn't include implementations of the various Fantasy Land "algebraic structures" like
Result, Either, Maybe, State, Reader, Future

Do folks typically just use the libraries listed on the Fantasy Land website here:

So If I wanted all of the above structures maybe I'd include and use:

Folktale: Result, Future
Sanctuary: Either, Maybe
Monastic: State
Zion: Reader

Just want to make sure there is no obvious single library that I should be using.


6 replies
Nils Riedemann

I'm sure there's a more elegant way to write this:

const seq = list => fns => r.call(r.apply(r.pipe, fns), list);

Still trying to wrap my head around currying, composing, piping etc.

@nocksock You can use R.pipeWith(R.identity) to do almost the same thing, but I think writing simple and readable code is more important than pursuing for point-free/curry code.
more readable version :)
const seq = R.curry((list, fns) => R.pipe(...fns)(list))
Nils Riedemann

writing simple and readable code is more important than pursuing for point-free/curry code.

@adispring Absolutely! However in my case it's just about embracing the pointfree style to fully grok it. This is just for a small utility package in a side project of mine that I specifically started to learn the ins and outs of FP. :D Using spread gave me a TS Error earlier, going to try yours after lunch! Thanks!

Andreas Herd
ahoy-hoy. How can I do a map(x -> x - min(...arr), arr) just with function composition. I tried to use converge but somehow getting the minimum to the map function didn't work
2 replies
Mike Vosseller
Hi all. I implemented a small game using Ramda. It's a connect-four command line game and my first attempt at functional programming. If anyone wants to review the code and give some feedback I'd love to hear it!
21 replies
Nils Riedemann
I'm currently working through the "Mostly Adequate to Functional Programming" (currently re-reading the monad-chapter) and I found the exercises to be really helpful. Is there a resource with more and similar exercises to understand Container Types and Monads better?
3 replies

I have a question about how to combine multiple functions with compose/pipe,
Is there any possibility to combine funcA and funcB in ramda way?
(or any reason we shouldn't do something like this.

Thanks in advance!

const funcA = (a, b) => a + b;
const funcB = (ab, c) => ab * c;

const funcC = (a, b, c) => {
  const ab = funcA(a, b);
  return funcB(ab, c)

funcC(1,2,3) // 9

Below is example using ramda REPL.

Andy Mac

@zydmayday if we look at funcB we see it's a 2-arity function. Remember that piping or composing functions only works when they're 1-arity or curried. But lets assume funcb is curried, then using compose would work, with one caveat, you have to call it like funcC(1,2)(3). That's because the result of compose is a 2-arity function (the same as funcA) - it'll just just throw away the 3rd argument. This will often work in the context of a larger program, if you're always calling it partially.

You can use a combinator to get around this. in this case it's a (f, g) => (a, b, c) => g(f(a,b), c) I don't think that one has a special name in FPland.

The ramda version of that combinator would be something like converge(funcB, [funcA, nthArg(2)])

1 reply
Ken Okabe
Hi, I wonder if ramda developers notice TC39 pipeline-operator is now Stage2 and people are upset against the decision of Hack-style proposal.
5 replies
RxJS author has just announced he considers the Hack proposal is not worth adopting, and will never cooperate with and ignore it.
Andy Mac
I'm thinking about making an atom (ide) package that functions like the ramdajs.com repl. I'd like to include options too, to include other popular FP packages. If anyone has any feature suggestions or is interested in helping, let me know.
Ken Okabe
TC39/proposal-pipeline-operator Hack-style |> hijacks Grouping operator ( ) https://dev.to/stken2050/the-current-tc39-proposal-pipeline-operator-hack-style-hijacks-grouping-operator-1dam Give me comments thanks.