/* Copyright (GPL) 2004 mchirico@users.sourceforge.net or mchirico@comcast.net
Simple lemon parser example.
Download:
http://prdownloads.sourceforge.net/souptonuts/lemon_examples.tar.gz?download
To compile this example see the Makefile. Or
this is what is taking place.
$ ./lemon example2.y
$ cat main_part2 >> example2.c
$ g++ -o ex2 -O2 -s -pipe example2.c
Next, run ./ex2
$ ./ex2
Which will give the following output:
Result.value=17 <---------------------------\
Result.n=4 |
Result.value=-9 |
Result.n=4 |
Result.value=78 |
Result.n=10 |
|
Now looking at a section of main_part2 |
we can see how 4 PLUS 13 in implemented. |
|
struct Token t0,t1; |
struct Token mToken; |
|
t0.value=4; |
t0.n=0; |
|
t1.value=13; |
t1.n=0; |
// Below 4 PLUS 14 ----------------- /
Parse (pParser, NUM, t0);
Parse (pParser, PLUS, t0);
Parse (pParser, NUM, t1);
Parse (pParser, 0, t0);
*/
%include {
#include <iostream>
#include "ex2def.h"
#include "example2.h"
}
%token_type {Token}
%default_type {Token}
%type expr {Token}
%type NUM {Token}
%left PLUS MINUS.
%left DIVIDE TIMES.
%syntax_error {
std::cout << "Syntax error!" << std::endl;
}
program ::= expr(A). {
std::cout << "Result.value=" << A.value << std::endl;
std::cout << "Result.n=" << A.n << std::endl;
}
expr(A) ::= expr(B) MINUS expr(C). { A.value = B.value - C.value;
A.n = B.n+1 + C.n+1;
}
expr(A) ::= expr(B) PLUS expr(C). { A.value = B.value + C.value;
A.n = B.n+1 + C.n+1;
}
expr(A) ::= expr(B) TIMES expr(C). { A.value = B.value * C.value;
A.n = B.n+1 + C.n+1;
}
expr(A) ::= expr(B) DIVIDE expr(C). {
if(C.value != 0){
A.value = B.value / C.value;
A.n = B.n+1 + C.n+1;
}else{
std::cout << "divide by zero" << std::endl;
}
} /* end of DIVIDE */
expr(A) ::= NUM(B). { A.value = B.value; A.n = B.n+1; }
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Mike Chirico, a father of triplets (all girls) lives outside of
Philadelphia, PA, USA. He has worked with Linux since 1996, has a Masters
in Computer Science and Mathematics from Villanova University, and has
worked in computer-related jobs from Wall Street to the University of
Pennsylvania. His hero is Paul Erdos, a brilliant number theorist who was
known for his open collaboration with others.
Mike's notes page is souptonuts. For
open source consulting needs, please send an email to
mchirico@gmail.com. All consulting work must include a donation to
SourceForge.net.
