http://d.puremagic.com/issues/show_bug.cgi?id=1245

           Summary: static foreach shouldn't define new scope and introduce
                    new variables
           Product: D
           Version: 1.014
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: baryluk@mpi.int.pl


import std.stdio;

void Code(x...)() {
        foreach (i, xi; x) {
                static if (xi != 0) { // dosn't works, see below
              //static if (x[i] != 0) { // workaround
                        writefln(xi);
                }
        }
}


void main() {
        alias Code!(1, 6, 0, 2, 5) c;
        c();
}

// staticforeachif.d(5): Error: expression xi != 0 is not constant // or does not evaluate to a bool

with workaround, it works, and display:
1
6
2
5
as needed

Imho foreach over tupple shouldn't introduce new scope and variables xi, but as static if be in the same scope (if needed you always can add { .. } and xi (second parameter in foreach), should be actually alias to x[i]

I'm using this in optimalisation of general code generators.


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smjg@iname.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |smjg@iname.com




------- Comment #1 from smjg@iname.com  2007-05-25 04:48 -------
Huh?  What is a "static foreach"?  If there's any reference to it in the spec, it isn't obvious.


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------- Comment #2 from baryluk@mpi.int.pl  2007-05-25 08:05 -------
http://www.digitalmars.com/d/tuple.html Looping section.
Foreach over tuple works like static foreach, and it is unrolled in compile
time.


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smjg@iname.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid




------- Comment #3 from smjg@iname.com  2007-05-25 11:49 -------
I see.

But I'm not sure I see how it would work to make foreach not define a scope in such circumstances.  OTOH, I agree that xi should be recognised as constant.


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shro8822@uidaho.edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |shro8822@uidaho.edu




------- Comment #4 from shro8822@uidaho.edu  2007-05-25 12:17 -------
The issue I have is that int the foreach loop the value of i gets pushed onto the stack. (I was looking at the ASM dump from DMD linux)

foreach(i, j; T!(1,2,3)
{
   asm{nop;};
}

should compeile to
nop;
nop;
nop;


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------- Comment #5 from baryluk@mpi.int.pl  2007-05-29 00:27 -------
Another example:

module staticforeach_switch;

import std.stdio;

template Tuple(E...) { alias E Tuple; }
alias Tuple!(101.0, 102.0, 103.0, 104.0) coef;

double f(int l, double x) {
   switch (l) {
     foreach (i, a_i; coef) {
        case i:
            //return x*a_i; // compiles and gives garbage
            return x*coef[i]; // works
      }
        default:
            assert(0);
   }
   assert(0);
}

void main() {
        writefln(f(3, 2.0)); // 2*104 = 208
}


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--- Comment #6 from Witold Baryluk <baryluk@smp.if.uj.edu.pl> 2009-11-18 21:41:58 PST ---
I just tested this both my codes (from "Description" and "Comment 5") in DMD
2.032, and they works correctly! (only switch isn't full optimal in asm, but
this not conected with this bug).

BCS's example with nop's is also not optimal, there are some operations on EBP
register:
        mov    dword ptr -034h[EBP],1
        nop
        mov    dword ptr -02Ch[EBP],2
        nop
        mov    dword ptr -024h[EBP],3
        nop
        mov    dword ptr -01Ch[EBP],5
        nop
        mov    dword ptr -014h[EBP],6
        nop
        mov    dword ptr -0Ch[EBP],7
        nop


I don't remember any changelog entry mentioning anything about foreach over tuples... Anyone want to enlighten me? :) And what about DMD 1.x?

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bearophile_hugs@eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bearophile_hugs@eml.cc
         Resolution|                            |FIXED


--- Comment #7 from bearophile_hugs@eml.cc 2010-04-12 17:52:10 PDT ---
This is now fixed in DMD 1.058 and 2.043.

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