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Date:	Fri, 15 Apr 2005 10:49:01 PDT7
From:	"Steven Levine" <steve53@earthlink.net >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: Progress--Step 3

In <200504151711.j3FHBxnQ022969@well.com>, on 04/15/05
at 10:12 AM, "Gregory W. Smith" said:

>We had a Programming SIG presentation about this and someone is still
>unclear about what was presented. My comment about a referee was an
>attempt to have Steve clarify what I took away from that presentation.
>And as I understood it

> GRAMMAR LEX --> C code

> C code from LEX YACC --> Parser

Both LEX and YACC take a language definition as input. Typically LEX is
used for the bottom end of the full language and YACC is used for the the
top end. The reason LEX and YACC are two separate tools has more to do
with unix programming style than any particular requirement.

Used together you get a tool that takes input and generates output. The
resulting tool might be a parser, but that's up to you.

Definitions of terms is important here, only to the extent that it ensures
we are all talking about the same thing. To me, a parser is not a
compiler. A parser just recognizes the defined language. A compiler
generates some sort of transformed output. Clearly the parser generate
outputs, but these are for internal use, so that's how I differentiate the
two.

IMNOSHO saying you can't build a PL/1 compiler using C is untrue, at best.
I can write C code to emulate any PL/1 construct. Whether or not writing
a PL/1 compiler in C will produce a compiler that performs well and
generates well optimized code is open for discussion. It depends more on
the talents of the compiler writers than the particular development tool.

Regards,

Steven

--
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"Steven Levine" MR2/ICE 2.67 #10183 Warp4.something/14.100c_W4
www.scoug.com irc.fyrelizard.com #scoug (Wed 7pm PST)
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