> Hi,
> Can u send me any documentation on LEMON that u have worked out.
> I have some queries also.....
> 1.Does LEMON work on Windows environment?
> 2.I tried but it is not.I heard that it works on Linux environment.I am
> trying to know why not on windows...can u give me some info about it
>
> I am reading the material u have suggested me but it did not have any
> information regarding to my queries.
>
> Can u mail me if u have made any documentation on LEMON.
>
Well, basically lemon works as follows:
1. It reads the definition of the parser from the input file
you give it as the first argument. From that it produces
a set of tables that implement the parser. This information
gets filled in in a template.
2. The result is a C file that you can use to parse (interpret)
your input.
3. What it does not do is split up the input into tokens. You
have to do that yourself.
I attach a small - not very efficient - example that shows a
few features of lemon.
As for your questions:
There is no reason it would not work on Windows: it is a
perfectly straghtforward C program, you get the source code
and compile it. One thing though: the template file must be
in the directory where you run the program, where the
executable lives or in the PATH.
(I am using it myself on Windows :). I am adapting it so that
it will produce Fortran code instead of C code. But that is
off topic.)
Here is my sample parser definition:
// expr.y
// Simple parser:
// expr = vaue + value + value + ...
%extra_argument {State *state}
%token_type {Token*}
%type term {int}
expr ::= firstterm plusterms . {
printf( "Result: %d\n", state->sum );
}
firstterm ::= term(T) . {
state->sum = T;
printf("First term: %d\n", T );
}
term(V) ::= NUMBER(N) . {
sscanf( N->token, "%d", &V );
printf("Term: %d -- %s\n", V, N->token );
}
plusterms ::= .
plusterms ::= plusterms plusterm .
plusterm ::= PLUS term(T) . {
state->sum = state->sum + T;
printf( "Result so far: %d\n", state->sum );
}
------
And here is the main program that includes the
resulting C code:
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
typedef struct {
char *token;
} Token;
typedef struct {
int sum;
} State;
#include "expr.h"
#include "expr.c"
int main( int argc, char *argv[] ) {
Token token[10];
State state;
void *pParser = (void *) ParseAlloc( malloc );
ParseTrace( stdout, ">>" );
token[0].token = "1"; Parse( pParser, NUMBER, &token[0], &state );
token[1].token = "+"; Parse( pParser, PLUS, &token[1], &state );
token[2].token = "2"; Parse( pParser, NUMBER, &token[2], &state );
token[3].token = "+"; Parse( pParser, PLUS, &token[3], &state );
token[4].token = "3"; Parse( pParser, NUMBER, &token[4], &state );
Parse( pParser, 0, &token[0], &state );
ParseFree( pParser, free );
return 0;
}
-----
One thing to note:
As the tokens are not always treated the moment they are passed
to the parser - this depends on the grammar and the moment in the
parsing process, you need to make sure that the tokens remain
available. I have done that in this silly program by using an
array of them. But a smarter program would use lemon's
abilities to destroy the tokens when ready.
Regards,
Arjen
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