Re: Introducing loopfusion: loop over any number of sequences of any single type.

[mratsim]

I've updated the package, it now supports in-place mutation of the inputs and 
sequence of different subtypes as input.

Here is a snippet of the syntax.
    
    
    import loopfusion
    
    block: # Simple
      let a = @[1, 2, 3]
      let b = @[11, 12, 13]
      let c = @[10, 10, 10]
      
      forEach x in a, y in b, z in c:
        echo (x + y) * z
      
      # 120
      # 140
      # 160
    
    block: # With index
      let a = @[1, 2, 3]
      let b = @[11, 12, 13]
      let c = @[10, 10, 10]
      var d: seq[int] = @[]
      
      forEach i, x in a, y in b, z in c:
        d.add i + x + y + z
      
      doAssert d == @[22, 25, 28]
    
    block: # With mutation
      var a = @[1, 2, 3]
      let b = @[11, 12, 13]
      let c = @[10, 10, 10]
      
      forEach x in var a, y in b, z in c:
        x += y * z
      
      doAssert a == @[111, 122, 133]
    
    block: # With mutation, index and multiple statements
      var a = @[1, 2, 3]
      let b = @[11, 12, 13]
      let c = @[10, 10, 10]
      
      forEach i, x in var a, y in b, z in c:
        let tmp = i * (y - z)
        x += tmp
      
      doAssert a == @[1, 4, 9]
    
    block: # With iteration on seq of different types
      let a = @[1, 2, 3]
      let b = @[false, true, true]
      
      forEach integer in a, boolean in b:
        if boolean:
          echo integer