Re: Fast enumeration

[Jens Ayton]

On Feb 7, 2011, at 10:52, Fred Kiefer wrote:

> I remember reading a nice little Macro (or rather two?) that
> encapsulated all the foreach semantics for systems that don't support
> it. This was in David's Objective-C Phrasebook and perhaps David could
> donate that to some Foundation/base header file. That way we will just
> need to keep that header up to date with regards tot eh different
> compilers and anybody could use fast enumerations whenever they are
> supported on their computer without adopting the code.

For reference, here's what I have now. The actual enumeration macros are about 
as hygienic as fake control flow statements can be, at the cost of requiring 
the iteration variable to be pre-declared. It requires C99 mode, but hey, it's 
2011.


/*  Fast enumeration (for (x in y) syntax) is supported in all Mac compilers
    when targeting 10.5 or later, and in gcc 4.6 with the GNU libobjc runtime.
    At the time of writing, GNUstep stable does not support gcc 4.6, but it
    already has support for the fast enumeration protocol in its collection
    classes.
    
    All release versions of clang support fast enumeration, assuming libobjc2
    or ObjectiveC2.framework is being used. We shall make that assumption.
    
    References:
        http://lists.gnu.org/archive/html/discuss-gnustep/2011-02/msg00019.html
        http://wiki.gnustep.org/index.php/ObjC2_FAQ
    -- Ahruman 2011-02-04
*/
#if OOLITE_MAC_OS_X
    #define OOLITE_FAST_ENUMERATION     OOLITE_LEOPARD
#else
    #if __clang__
        #define OOLITE_FAST_ENUMERATION 1
    #elif defined (__GNU_LIBOBJC__)
        #define OOLITE_FAST_ENUMERATION (OOLITE_GCC_VERSION >= 40600)
    #endif
#endif

#ifndef OOLITE_FAST_ENUMERATION
#define OOLITE_FAST_ENUMERATION         0
#endif


/*  Enumeration macros:
    foreach(VAR, COLLECTION) enumerates the members of an array or set, setting
    the variable VAR to a member on each pass.
    foreachkey(VAR, DICT) enumerates the keys of a dictionary the same way.
    
    Example:
        id element = nil;
        foreach (element, array)
        {
            OOLog(@"element", @"%@", element);
        }
    
    These are based on macros by Jens Alfke.
*/
#if OOLITE_FAST_ENUMERATION
#define foreach(VAR, COLLECTION)    for(VAR in COLLECTION)
#define foreachkey(VAR, DICT)       for(VAR in DICT)
#else
#define foreach(VAR, COLLECTION)    for (NSEnumerator *ooForEachEnum = 
[(COLLECTION) objectEnumerator]; ((VAR) = [ooForEachEnum nextObject]); )
#define foreachkey(VAR, DICT)       for (NSEnumerator *ooForEachEnum = [(DICT) 
keyEnumerator]; ((VAR) = [ooForEachEnum nextObject]); )
#endif



-- 
Jens Ayton