ramda/ramda

Practical functional Javascript

coffeefedora

@coffeefedora

I wonder if I setup the vals right, i can use mergeAll?

Dmitri Zaitsev

@dmitriz

Object merge can now be done with spread

but of course you can use ramda if you prefer

coffeefedora

@coffeefedora

not sure is spread is in IE 11

and what does ramda call spread? i looked for that

Dmitri Zaitsev

@dmitriz

ramda has some merging functions but I have no idea since I just use spread

but it may not be supported by some old browsers, you need to check that

or use ramda, if that is supported

but it doesn't change on the issue of purity

in principle, you can still write non-pure functions in functional style of course

Dmitri Zaitsev

@dmitriz

x => array => {array.push(x); return array}

coffeefedora

@coffeefedora

right, which is what i do for some tree stuff

Dmitri Zaitsev

@dmitriz

but notice my function returns

so you can return your tree

Dale Francis

@dalefrancis88

@dmitriz compose/pipe are actually just wrappers around reduceRight(B)/reduce(B)

the power in combinators really comes into play further down the track as you have all you're small utility functions and can start to bring them together. converge is where i've seen some people begin to reach for the power of combinators

Dmitri Zaitsev

@dmitriz

@dalefrancis88 Doesn't convergehave the limitation of all functions in the array accepting the same arguments?

For instance, converge(f, [g,h])(x,y)requires both g and h to accept (x,y).

Dmitri Zaitsev

@dmitriz

Also maybe both compose and converge can be unified into arbitrary pipelines containing functions or arrays of functions. Which would be wrappers around reduce as you point out, so we only need a pipe(a,b), where each of a,b is either a function or an array of functions.

akillingbeck89

@akillingbeck89

Hey guys, having a strange issue with Ramda here...basically I'm trying to remove an item from an array if it's already there, and add it if it's not. I replaced the ramda code with standard JS and it worked instantly, unsure what's wrong with the setup here:

const newSelections = R.pipe(
        R.path(['selectedSections']),
        R.ifElse(R.contains(payload), R.without(payload), R.append(payload))
      )(state)
      return R.assoc('selectedSections', newSelections, state)

So without should remove payload if selectedSections contains it, I've debugged the input, it's all fine and correct. Also thought it might be a case of modifying the original array while iterating, so I attempted a deep clone of selectedSections too (which didn't work)

Riku Tiira

@rikutiira

first argument of R.without should be an array of values you want to omit

akillingbeck89

@akillingbeck89

Sorry, I should have mentioned, it generally works, but when selecting a section whose string might contain a sub-string of others, all of the others get deselected to.

Riku Tiira

@rikutiira

if your payload is an array then not sure what’s wrong there

also, you could replace the whole thing with return R.evolve({ selectedSections: R.ifElse(R.contains(payload), R.without(payload), R.append(payload)) }, state)

akillingbeck89

@akillingbeck89

Yeah it is an array, ok cheers I'll give that a go

Cool that worked, thanks :)

Bijoy Thomas

@bijoythomas

hello, is there a combinator whose signature is like: (a => b => c) => (x => a) => (y => b) => x => y => c .. kinda like useWith or can this be built from the basic combinators?

Dale Francis

@dalefrancis88

@bijoythomas not in Ramda but there is one in crocksit's called compose2 https://crocks.dev/docs/functions/combinators.html#compose2

Bijoy Thomas

@bijoythomas

@dalefrancis88 thank you

Dale Francis

@dalefrancis88

np :)

mitcho

@mitchoSR_twitter

anyone know of an R function thats like reduce but just repeats x times something like this, seems very useful for generating data

const reduceXTimes = (fn,init) => num => {
    for(let i = 0; i < num; i++)
        init = fn(init,i);   
    return init;
}

also does anyone know of a higher order function that takes 2 arrays and supplies one to a callback that iterates over the other and reduces

dont need them, just curious if they exist

Kurt Milam

@kurtmilam

@mitcho : https://ramdajs.com/docs/#times

mitcho

@mitchoSR_twitter

neato, thank you

Kurt Milam

@kurtmilam

Not sure exactly how the second one is supposed to work.

Brad Compton (he/him)

@Bradcomp

There's also R.reduceWhile

Charles Hughes

@chughes87

Hey all, I'm trying to use pipe with ifElse. I'm trying to define a pipeline and utilizing it conditionally with ifElse. However, the default arity of pipe seems to be 3 for some reason and that is messing with the ifElse... For more context on ifElse's arity behavior: ramda/ramda#2654. Is there some workaround for this that isn't super ugly? Im enforcing arity of one with an inline (input) => pipeFn(input) right now

mitcho

@mitchoSR_twitter

@Bradcomp thanks, that looks great too

Ben Briggs

@ben-eb

@chughes87 You can use o which is unary composition, note it will only accept two functions unlike pipe which is variadic

Also there is the unary helper which you could do instead of your arrow

Charles Hughes

@chughes87

great thank you for the tips!

coffeefedora

@coffeefedora

is there a way to define a function with all of its params, but not invoke till later?

var ff = function(a,b) { return a + b; };

var add23 = ff(2,3); // don't invoke yet

add23(); // ok invoke.

i mean, right now i'm doing var add23 = function() { return ff(2,3); };

but the ff func is a curried function, and i just kinda wondered if there was a pretty way. I am using this for effects, so I have a generic function I pre-bind values, so I can call it "toggleSaveButtons" vs "animate(element, startClass, endClass, ..)"

and maybe I should read the doc on R.partial right. I was invoking it wrong :(

heh

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