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From: tneff@bfmny0.UUCP (Tom Neff)
Newsgroups: comp.sys.intel
Subject: Re: PLM vs. C for 80286/80386
Keywords: PLM C
Message-ID: <14395@bfmny0.UUCP>
Date: 9 Jun 89 05:33:17 GMT
References: <598@philtis.UUCP> <126@tridom.uucp> <5711@lynx.UUCP>
Reply-To: tneff@bfmny0.UUCP (Tom Neff)
Organization: ^
Lines: 47

In article <5711@lynx.UUCP> m5@lynx.UUCP (Mike McNally) writes:
>The claim made that PL/M switch statements are always branch table
>based is true, but of course that's easy when the case labels are
>*always* 0 through N.  And of course, if the selector is out of range,
>the results are undefined (no such thing as default:).  Structures
>within structures?  Sorry.  Two dimensional arrays?  Sorry.  Macros
>with arguments? Sorry.

Truth Squad Dept.: 

 * The original 'switch' claim had to do with iC, not PL/M, and the
   claim was that elseif was used when a jump table should have been.
   PL/M certainly uses jump tables on DO CASE -- this wasn't a claim,
   it's just a fact.

 * PL/M doesn't range check DO CASE for you automatically, it's your
   responsibility.  This demands programmer responsibility but allows
   for extra speed in the case where the o/r *truly* "can't happen".

 * Structures within structures - available since PL/M 2.7 (1987).

 * 2-d arrays aren't available in the sense of A(i,j) but you have
   always been able to do this elegantly with structure arrays:

	DECLARE
		table (20) STRUCTURE(
			col	(50) WORD);

	table(i).col(j) = x+y*5;

   Now with nested structures (for the last two years) you can generalize
   this to N-dimensional arrays if the mood strikes.

 * Macros with arguments are sadly missing from PL/M (all you get is the
   simple-replacement LITERALLY facility), however one is at liberty to 
   preprocess PL/M source with either MPL86 or (now) the iC-x86 
   preprocessor before compiling.  In fact I suspect the latter will
   become popular - you can have all the #defines you want and still
   get valid PL/M to compile.  I use MPL86 based "macro PL/M" for a
   number of projects - it's the best way to automatically generate
   count precedent string constants, for instance.

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Tom Neff				UUCP:     ...!uunet!bfmny0!tneff
    "Truisms aren't everything."	Internet: tneff@bfmny0.UU.NET