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4133 :: for loop with more items

• RWS (orginal) [2018-08-16T21:06:27+02:00] view original

  Hi there. I'm doing some experiments with Nim. Can anyone explain how this code:

  for x, y  in [0..10, 0..10]:
    echo(x)
    echo(y)
  Run

  gives this output:

  0 (a: 0, b: 10) 1 (a: 0, b: 10)

  and is there a way to work this 2 or more items in a for loop? Thx

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• emekoi (orginal) [2018-08-16T23:17:14+02:00] view original

  the for loop is iterating over the array and not the ranges in the array. afaik you can't iterate over two ranges like that in nim.

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• kaushalmodi (orginal) [2018-08-16T23:58:49+02:00] view original

  This will help you understand that code better:

  import strformat, typetraits
  let r = [0 .. 3, 0 .. 3]
  echo fmt"r = {r}, of type `{$r.type}'"
  
  for x, y  in r:
    echo fmt"x = {x}, of type `{$x.type}'"
    echo fmt"y = {y}, of type `{$y.type}'"
  Run

  Output:

  
  r = [(a: 0, b: 3), (a: 0, b: 3)], of type `array[0..1, HSlice[system.int, system.int]]'
  x = 0, of type `range 0..1(int)'
  y = (a: 0, b: 3), of type `HSlice[system.int, system.int]'
  x = 1, of type `range 0..1(int)'
  y = (a: 0, b: 3), of type `HSlice[system.int, system.int]'
  Run

  This is probably what you wanted:

  import strformat, typetraits
  for x in 0 .. 3:
    for y in 0 .. 3:
      echo fmt"x = {x}, of type `{$x.type}', y = {y}, of type `{$y.type}'"
  Run

  Outputs:

  
  x = 0, of type `int', y = 0, of type `int'
  x = 0, of type `int', y = 1, of type `int'
  x = 0, of type `int', y = 2, of type `int'
  x = 0, of type `int', y = 3, of type `int'
  x = 1, of type `int', y = 0, of type `int'
  x = 1, of type `int', y = 1, of type `int'
  x = 1, of type `int', y = 2, of type `int'
  x = 1, of type `int', y = 3, of type `int'
  x = 2, of type `int', y = 0, of type `int'
  x = 2, of type `int', y = 1, of type `int'
  x = 2, of type `int', y = 2, of type `int'
  x = 2, of type `int', y = 3, of type `int'
  x = 3, of type `int', y = 0, of type `int'
  x = 3, of type `int', y = 1, of type `int'
  x = 3, of type `int', y = 2, of type `int'
  x = 3, of type `int', y = 3, of type `int'
  Run

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• kaushalmodi (orginal) [2018-08-17T00:09:48+02:00] view original

  But this is Nim, you can do Anything (TM) :D

  iterator pairs(r: array[0 .. 1, HSlice[system.int, system.int]]): tuple[a: int, b: int] =
    for r1 in r[0]:
      for r2 in r[1]:
        yield (r1, r2)
  
  for x, y in [0 .. 3, 0 .. 3]:
    echo x, " ", y
  Run

  Outputs:

  
  
  0 3
  1 0
  1 1
  1 2
  1 3
  2 0
  2 1
  2 2
  2 3
  3 0
  3 1
  3 2
  3 3
  Run

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• mratsim (orginal) [2018-08-17T13:51:09+02:00] view original

  Maybe Slice should use (slice_start, slice_end) for naming instead of (a, b).

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• kaushalmodi (orginal) [2018-08-17T14:14:30+02:00] view original

  The a, b are not actually start/end values. They are arbitrary elements from the first and second slices (r[0] and r[1]).

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• RWS (orginal) [2018-08-17T18:32:28+02:00] view original

  Thx you all. I' was trying to find a way to make the same of this C# code with a similar syntax:

  for (int x = 0, y = 0; x <= 10 && y <= 10; x++, y++)

  {

  Console.WriteLine(x + y);

  }

  but i got lost on the way

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