Question

I’m trying to wrap my head around functional programming in ruby and there doesn’t seem to be much good documentation out there.

Essentially, I’m trying to write a combine function that would have a Haskell type signature of:

[a] -> [a] -> (a -> a -> a) -> [a] 

So

combine([1,2,3], [2,3,4], plus_func) => [3,5,7] combine([1,2,3], [2,3,4], multiply_func) => [2,6,12] 

etc.

I found some stuff about using zip and map but that feels really ugly to use.

What would be the most ‘ruby’ way of implementing something like this?

Answer 1

Well, you said you know about zip and map so this probably isn’t helpful. But I’ll post just in case.

def combine a, b     a.zip(b).map { |i| yield i[0], i[1] } end  puts combine([1,2,3], [2,3,4]) { |i, j| i+j } 

No, I don’t find it beautiful either.

edit – #ruby-lang @ irc.freenode.net suggests this:

def combine(a, b, &block)     a.zip(b).map(&block) end 

or this, if you want to forward args:

def combine(a, b, *args, &block)     a.zip(b, *args).map(&block) end