Xref: utzoo comp.lang.c:36667 comp.software-eng:4957
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!aspect!dave
From: dave@aspect.UUCP (Dave Corcoran)
Newsgroups: comp.lang.c,comp.software-eng
Subject: Re: Source File Organization
Summary: yet another possible m4 solution
Message-ID: <8001@aspect.UUCP>
Date: 1 Mar 91 15:27:25 GMT
References: <1991Feb26.045242.23453@rfengr.com>
Followup-To: poster
Organization: Aspect Telecommunications, San Jose, Ca
Lines: 62

In article <1991Feb26.045242.23453@rfengr.com>, rfarris@rfengr.com (Rick Farris) writes:
> I have an enumerated type:
> 
> typedef enum { A, B, C, D } CMD;
> 
> and a corresponding array of ascii representations :
> 
> char ltrs[] = { 'A', 'B', 'C', 'D' };
> 
> Suppose I add a new CMD, "Z", is there any way to ensure
> that ltrs[] is updated?
> 

run this through m4 you might be pleasantly suprised; although anyone
maintaining your code may what to drop the adjective "pleasantly" :-)

define(awkdef,
	`syscmd((echo ' '$2' | sed 's/^(//;s/^)//' `>/tmp/am_$1))'
	`define($1,`syscmd(awk $'`2 -f /tmp/am_$1 ifelse($'`1,,,<<@@
$'`1
@@))')'
)

awkdef(xx,(  # note the leading (
	BEGIN {printf "enum {"}
	{
	for (i=1;i<=NF;i++) printf "%s,",$i
	}
	END {print "} CMD;"}
))	/* note the first paren MUST be flush against the left margin */


/* note the '\'' construct is needed to get a single ' in the output */

awkdef(yy,(
	BEGIN {printf "char ltrs[] = {"}
	{
	for (i=1;i<=NF;i++) printf "'\''%s'\'',",$i 
	}                                           
												
	END {print "};"}
))

define(letters,`xx($1)yy($1)')
letters(A B C D E F G H I J K L M)

/* if you need conditional compliation */

define(`letters',`ifdef(`header_file',`yy($1)',`xx($1)')')

/* this next line would be in a .c source */
letters(A B C)

/* these two would be in a .h header */
define(header_file)

letters(A B C)

-- 
David Corcoran		      -@@
uunet!aspect!dave	        ~
In a society where anything goes eventually everything will.