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sat_parser.cpp
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sat_parser.cpp
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#include <cstdio>
#include <cstdlib>
#include <iostream>
using namespace std;
struct bexpr {
char val;
char op;
char neg;
bexpr *expr;
};
void err()
{
printf("syntax error\n");
exit(1);
}
char* skip(char* s)
{
//while (*s == ' ' || *s == '\n' || *s == '\t') ++s;
//printf("skip: @%c\n", *s);
return s;
}
// grammar:
// <S>: <bool> <op> <S> | <bool> | <t>
// <bool>: '~' <bval> | <bval>
// <bval>: '1' | '0' | 't' | 'f' | 'T' | 'F'
// <op>: '^' | '&' | '|'
void B(bexpr* expr, char** prog)
{
char* s = *prog;
s = skip(s);
if (!s || !(*s)) err(); // <bool> does not allow <t>
printf("B(): @%c\n", *s);
switch (*s) {
case '~': {
expr->neg = 1;
++s;
}
case '1':
case '0':
case 't':
case 'f':
case 'T':
case 'F':
expr->val = *s;
++s;
break;
default:
err();
}
*prog = s;
}
void OP(bexpr* expr, char** prog)
{
char *s = *prog;
s = skip(s);
if (!s || !(*s)) err(); // <op> does not allow <term> either
printf("OP(): @%c\n", *s);
switch (*s) {
case '^':
case '&':
case '|':
expr->op = *s;
++s;
break;
default:
err();
}
*prog = s;
}
#define _T(expr,prog) \
if (!(*prog) || !(**prog) || (**prog==';')){\
expr->op=';';\
return 1;}
bool T(bexpr* expr, char** prog)
{
_T(expr,prog);
*prog = skip(*prog);
_T(expr,prog);
return 0;
}
void S(bexpr* expr, char** prog)
{
printf("S(): check\n");
if (T(expr,prog)) return; // the <t> case
printf("S(): parsing B()\n");
B(expr, prog);
if (T(expr,prog)) return;
printf("S(): parsing OP()\n");
OP(expr, prog);
if (T(expr,prog)) err(); // strict check for next <S>, no term allowed here
expr->expr = new bexpr;
printf("S(): parsing S()\n");
S(expr->expr, prog);
}
void RPN_print(bexpr * expr)
{
if (expr->op == ';') {
printf("%c", expr->val);
return;
}
printf("(");
printf("%c ", expr->op);
if (expr->neg == '~') printf("%c",expr->neg);
printf("%c ", expr->val);
if(expr->expr)
RPN_print(expr->expr);
printf(")");
}
void bexpr_free(bexpr* expr)
{
bexpr* next;
while ( expr->op != ';' )
{
next = expr->expr;
delete expr;
expr = next;
}
delete expr;
}
int main()
{
char * s;
size_t len;
cin >> len;
s = (char*) malloc(len);
memset(s, '\0', len);
scanf("%s", s);
++s;
printf("input: %s\n", s);
bexpr *expr = new bexpr;
S(expr, &s);
RPN_print(expr);
puts("");
bexpr_free(expr);
return 0;
}