Syntax proposal: call it forZip

[krux02]

There is one big reason why I don't like the forEach, and that is my Scala background.

val seq1 = Seq(1,2,3)
val seq2 = Seq(4,5,6)
for( a <- seq1, b <- seq2 ) {
    println(a,b)
}

val seq1 = Seq(1,2,3)
val seq2 = Seq(4,5,6)
is compiled to:

seq1.forEach(a => seq2.forEach(b => println(a,b))

This is basically just a nested loop with λ-expressions as the body. Zip would be the following:

val seq1 = Seq(1,2,3)
val seq2 = Seq(4,5,6)

for( (a,b) <- zip(seq1, seq2) ) {
    println(a,b)
}

I don't say you should take over or try to mimic the Scala syntax, but I think you should take over the names. Please call it to something that has both for and zip in the name. forEach has already a very specific meaning in my head, and it is not what you are doing with forEach. Also c++ has already std::foreach and it means the same as in scala (it's just useless in c++, but that is an opinion and a different topic). And I don't think it is a bad idea to adopt to scala naming conventions (I personally really liked them for the most part)

(please don't kill me if the scala snippents don't compile, I did not program scala for years, and I have no compiler on this machine)

[mratsim]

Interesting name, I will look into what other languages (Haskell, F#) do like I did here mratsim/Arraymancer#41.

I'm also looking for a name that does "forZipReduce/forZipFold" but I'm at a complete loss.

[krux02]

Well with your last part I can help you, call it mapReduce.

[narimiran]

forEach can be also used with just one container (let x = forEach(x in a): x + 10), and in that case forZip is not a good name.

My proposition:

forAll

It makes sense both in the one container and multiple container scenarios.

Thoughts?

[krux02]

you can also call it, innerJoin and outerJoin if you want so. outerJoin would be the classical nested for loop.

[mratsim]

forAll looks great to me, it's short, isn't loaded like forEach, apply to single container scenario, rolls nicely on the tongue and reminds mathematical notation (∀x ∈ @[1,2,3], y ∈ @[4, 5, 6], read for all x in @[1,2,3] and y in @[4, 5, 6]).

forAny or forEvery are another alternatives but LaTeX choose \forall so I guess it wins :P

[mratsim]

On a second note, forAll might imply cartesian product:

forAll x in [1, 2, 3], y in [4, 5, 6]:
  echo (x, y)

# (1, 4)
# (1, 5)
# (1, 6)
# (2, 4)
# (2, 5)
# (2, 6)
# (3, 4)
# (3, 5)
# (3, 6)

[narimiran]

In Julia there is a similar syntax for Cartesian product, but if that is "confusing", it would still be even if you use any other word.

We (most languages?) have nested loops for Cartesian products.

[krux02]

I would like to mention that zip on it's own is not hard:

import macros

iterator zip[T,U](a: openArray[T]; b: openArray[U]): tuple[a:T, b:U] =
  let N = max(a.len, b.len)
  var i = 0
  while i < N:
    yield((a[i], b[i]))
    i.inc

let seq1 = [1,2,3,4]
let seq2 = [3,4,5]

for x, y in zip(seq1, seq2):
  echo x, " - ", y

But zipping iterators is hard in nim. And when you want an index with your zip, well it's gonna be ugly.

[mratsim]

After pondering for a while. It's done! forEach is now forZip.