on :: (b -> b -> c) -> (a -> b) -> a -> a -> c

[Bradcomp]

While the general useWith and converge from Ramda aren't very well typed, I do find them to be useful functions. One of my main use cases for useWith is to emulate Haskell's on function (this is also known as the psi combinator).

Example:

//Point :: {x, y}
const x = prop('x');

//Point -> Point -> Number
const leftmost = on(min, x);
const rightmost = on(max, x); 

I struggle with the parameter order for this function. In Haskell it's typically used in infix form:

leftmost = min `on` x

As a result, I generally define it using the signature above, even though there could be an argument made that the opposite order makes just as much sense.

Is there enough interest for this to be part of Sanctuary?

[davidchambers]

Is there enough interest for this to be part of Sanctuary?

This function seems useful to me. Would you like to submit a pull request?

I think the type signature you provided is missing one a ->, by the way.

[Bradcomp]

Thanks! I was missing the a. I will work on a PR.