proplogic.y

%{
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include "proplogic.h"

/* prototypes */
nodeType *opr(int oper, int nops, ...);
nodeType *id(int i);
nodeType *con(int value);
void freeNode(nodeType *p);
int ex(nodeType *p);
int yylex(void);

void yyerror(char *s);
int sym[26];                    /* symbol table */
%}

%union {
    char sIndex;                /* symbol table index */
    nodeType *nPtr;             /* node pointer */
};

%token <sIndex> VARIABLE 
%token TRUE
%token FALSE

%left NOT EQUIV OR AND IMPLIES 

%type <nPtr> formula term literal 

%%


formula:
         formula           { $$ = $1;}
        | term '|' formula   {$$ = opr('|', 2, $1, $3); } 
        | 
        ;

term:
         literal                          {$$ = $1; } 
       |   term '&' term                   { $$ = opr('&', 2, $1, $3); }
       ;


literal:
      VARIABLE          { $$ = id($1); }
    | '!' literal      {$$ = opr('!', 1, $2); }
    ;

%%

#define SIZEOF_NODETYPE ((char *)&p->con - (char *)p)

nodeType *con(int value) {
    nodeType *p;
    size_t nodeSize;

    /* allocate node */
    nodeSize = SIZEOF_NODETYPE + sizeof(conNodeType);
    if ((p = malloc(nodeSize)) == NULL)
        yyerror("out of memory");

    /* copy information */
    p->type = typeCon;
    p->con.value = value;

    return p;
}

nodeType *id(int i) {
    nodeType *p;
    size_t nodeSize;

    /* allocate node */
    nodeSize = SIZEOF_NODETYPE + sizeof(idNodeType);
    if ((p = malloc(nodeSize)) == NULL)
        yyerror("out of memory");

    /* copy information */
    p->type = typeId;
    p->id.i = i;

    return p;
}

nodeType *opr(int oper, int nops, ...) {
    va_list ap;
    nodeType *p;
    size_t nodeSize;
    int i;

    /* allocate node */
    nodeSize = SIZEOF_NODETYPE + sizeof(oprNodeType) +
        (nops - 1) * sizeof(nodeType*);
    if ((p = malloc(nodeSize)) == NULL)
        yyerror("out of memory");

    /* copy information */
    p->type = typeOpr;
    p->opr.oper = oper;
    p->opr.nops = nops;
    va_start(ap, nops);
    for (i = 0; i < nops; i++)
        p->opr.op[i] = va_arg(ap, nodeType*);
    va_end(ap);
    return p;
}

void freeNode(nodeType *p) {
    int i;

    if (!p) return;
    if (p->type == typeOpr) {
        for (i = 0; i < p->opr.nops; i++)
            freeNode(p->opr.op[i]);
    }
    free (p);
}

void yyerror(char *s) {
    fprintf(stdout, "%s\n", s);
}

int main(void) {
    yyparse();
    return 0;
}