while(0) ?

[CiNN]

#define R(l,r,i) do { l ^= p[i]; r ^= F(l); } while(0) why a while(0) ? :doh:

[toxcct]

useless so... but avoid using such a macro in your code...

---

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VCalc 3.0 soon...]

[Michael Dunn]

The do/while is there to provide a block. Without the do/while, this code:

if (somefunc())
R(a,b,c);

wouldn't give the right behavior because only the first statement would be inside the if block. --Mike-- Visual C++ MVP :cool: LINKS~! Ericahist | NEW!! PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

[toxcct]

but it could have provided these instructions into a block ( { } ) without do/while...

#define R(l,r,i) { l ^= p[i]; r ^= F(l); }

---

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VCalc 3.0 soon...] -- modified at 4:49 Wednesday 8th February, 2006

[Stephen Hewitt]

Not in all cases. Here's two versions of a macro: #define FOO1(n) { return n; } #define FOO2(n) do { return n; } while(0) Now given these two macros this will not complile:

if ( 1 )
  FOO1(1);
else
  return 0;

But this will:

if ( 1 )
  FOO2(1);
else
  return 0;

So there is method to the madness. Steve

[toxcct]

:-O oh, my mistake... yeah, the problem comes from the **;** following the expansion of the macro... a ; cannot come just after a } (except in a user-defined type definition - class, struct, enum, union...)

---

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VCalc 3.0 soon...]