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From: edw@ius2.cs.cmu.edu (Eddie Wyatt)
Newsgroups: comp.compilers,comp.unix.questions
Subject: Re: lex/yacc question
Message-ID: <1131@ius2.cs.cmu.edu>
Date: Wed, 29-Apr-87 01:53:55 EDT
Article-I.D.: ius2.1131
Posted: Wed Apr 29 01:53:55 1987
Date-Received: Sat, 2-May-87 02:38:18 EDT
References: <558@ima.UUCP>
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In article <558@ima.UUCP>, johnl@ima writes:
>[any easy way to make a listing in an assembler written in yacc and lex?]

Try production rules of the form

%term 	LEXDEFADDRESS	LEXDEFDATA COLON

addrprod 	: 	address COLON data LEXDEFNEWLINE
			{   generate_code ($1,$3); 
			   /* write code at end of production.
			      If you want, make generate_code
			      smart so that it buffers output
			      and writes only when the buffer is
			      full. */ }
		;

address		:	LEXDEFADDRESS
			{ $$ = make_address(); 
			  /* read the chars from yytext[]
			     and convert them into an address */ }
		;

data		:	LEXDEFDATA
			{ $$ = make_data();
			  /* read the chars from yytest[]
			     and convert them into data */ }
		;

I assume that your production is of the form:

addrprod	: 	LEXDEFADDRESS COLON LEXDEFDATA


in which case, any semantic rules will not be executed until
the lex symbol LEXDEFDATA is identified hence the chars that make
up the lex symbol LEXDEFADDRESS are lost to the parser (I know you've
hacked it so the lex code takes care of it, yuk).

General comment, lex and yacc are probably too powerful for writing
an assembler.  You will pay for all the generality of lex and
yacc in how fast your assembler runs.
	Eddie Wyatt, edw@ius2.cs.cmu.edu
[Lex might slow you down, but I have never, ever, seen a compiler where
hand-coding the parser rather than using yacc would make the compiler
noticably faster.  Yacc parses pretty fast, and parsing isn't that big a
part of compile time anway.  -John]
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