Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!samsung!uunet!hsi!genly!chris
From: chris@genly.UUCP (Chris Hind Genly)
Newsgroups: comp.sys.amiga
Subject: Re:  Lattice/SAS C  5.10 HERE!
Message-ID: <chris.6036@genly.UUCP>
Date: 24 Aug 90 20:50:11 GMT
References: <14874@shlump.nac.dec.com>
Lines: 117

>In article <1990Aug23.052447.24545@zorch.SF-Bay.ORG>, xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) writes...
>So tell me, does it still do a no-warning, no guru, stone cold system
>crash, trashing Rad:, if you try to do/use a 30 line #define?

>In article <14874@shlump.nac.dec.com> barrett@meridn.enet.dec.com (Keith Barrett) writes:
>Standard C coding practice recommends that a define should fit in 1 line
>of 80 characters; I think you got what you deserved. You're not the type
>to sue a ladder company because the instructions did not state "don't
>place the ladder in mud" and you did and fell, are you? :-)

I see the smiley, but I assume it only applies to the preceding
sentence, not the whole paragraph.

First I have to object to "you got what you deserved."  A compiler
should not crash when it runs into a limitation.  This is clearly a
bug and should be fixed.

Second, Multi-line macros are legitimate in C.  I use them all the
time.  As an example of a useful multi-line macro see the code below. 
Macros are wonderful because they let you "escape from the language". 
C does not directly support iteration abstraction.  With macros I can
write my own.  C does not support inlining.  With macros I can do my
own inlining.  In each case the macros are usually longer than one
line.

====================================================================
/*
 * File iterators
 *
 * 8/25/90     Chris Hind Genly     chris@genly.uucp
 *
 * No rights reserved.
 *
 */
#ifndef file_h
#define file_h

#ifndef stdin
#include <stdio.h>
#endif

#include <proto/dos.h>
#include <libraries/dos.h>

/*
 * Iterate through all files in a directory.
 *
 * The user declares dir as either a character pointer or character array.
 * It should be set to a directory path string.
 * The macro declares fi, and path.  Fi is the Amiga file info block.
 * Path is a char array containing the path to a file in the dir.
 * Fi and path may be referenced in the body of the for.
 * Break and continue are permitted inside this iterator.
 *
 * Example:
 *
 *    FOR_ALL_FILES("c:", fi, path) {
 *        printf("%s: %d\n", path, fi->fib_Size);
 *    } END_FOR_ALL_FILES;
 */

#define FOR_ALL_FILES(dir, fi, path) \
{ \
    BPTR lock; \
    static struct FileInfoBlock fis, *fi=&fis; \
    int ok; \
    char path[200], *sep; \
\
    switch(dir[strlen(dir)-1]) { \
    case '/': case ':': sep = ""; break; \
    default: sep = "/"; break; \
    } \
\
    lock = Lock(dir, ACCESS_READ); \
    if (lock == 0) { \
        fprintf(stderr, "snews: unable to lock %s\n", dir); \
        exit(1); \
    } \
\
    ok = Examine(lock, fi); \
    while(ok = ExNext(lock, fi)) { \
        strcpy(path, dir); \
        strcat(path, sep); \
        strcat(path, fi->fib_FileName);
        
#define END_FOR_ALL_FILES        \
    }                            \
                                 \
    UnLock(lock);                \
}

/*
 * Iterate through all directories of a directory.
 *
 * Same as above, except the body is only executed for directories.
 */
 
#define FOR_ALL_DIRS(dir, fi, path) \
    FOR_ALL_FILES(dir, fi, path) \
        if (fi->fib_DirEntryType <= 0) continue;
        
#define END_FOR_ALL_DIRS \
    END_FOR_ALL_FILES


#endif
====================================================================


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