Curry === is problematic

[Katja Lutz]

First off, i like your work! Its really cool to learn fp style without reading through dozens lines of code :).

I know you copied the curry function from a gist comment 😄 , i took some time to learn how it works and notices a problem - especially when its used together with reduce

Problem in one sentence: If the curried function is called with too many arguments, it will return a new curried function instead of calling the final function. Also the new curried function will now return again a new curried function for every further attempt.
https://github.com/selfrefactor/rambda/blob/master/modules/curry.js#L4

...
o.length === f.length
...

A basic example (ES6):

const add = curry((n, n2) => n + n2
add(1, 2, 3)
// result: function
// desired: 3

Reduce example:

const add = curry((n, n2) => n + n2)
reduce(add, 0, [1, 2, 3])
// result: function

Reduce calls the add function not only with acc and value, but also with index and array
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

• One way to fix it, would be to change o.length === f.length to o.length >= f.length
• An alternative would be to change the reduce function in the way, that it only calls with acc and value, (Ramda does it like that: http://ramdajs.com/0.23.0/docs/#reduce)

[Dejan Toteff]

I appreciate your nice words, but mostly catching these strange behaviors.

Back to business - I have edited curry upon your suggestion. and both of the above examples are included in the tests.

Just want to ask you, is there still a need for a change in reduce in the context that your reduce example now is working correctly?

Sorry, but I fail to fully understand the issue with reduce and I'll be grateful, if you help me out.

[Katja Lutz]

Thanks for the fast feedback and changes!

The approach to change reduce was just thought as an alternative - rather bad alternative because the callback of builtin map also gets idx and array. There is no bug or so in reduce! Actually I noticed the bug in curry because I was trying around with reduce and a curried function.

In Ramda functions like reduce and map dont provide idx and array to the cb, actually they had a long discussion about this: ramda/ramda#452

In my opinion both ways (with and without idx and array) are perfectly fine, the library author should decide which one is the right ;).

[Dejan Toteff]

Thank you for the detailed explanation.

I think I will go with the current state and leave it as it is.

I am closing the issue now.