git @ Cat's Eye Technologies Philomath / master src / formula.c
master

Tree @master (Download .tar.gz)

formula.c @master — raw · history · blame 

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
#include <stdio.h>
#include <stdlib.h>

#include "formula.h"

struct formula *
mk_formula(int type, const char *name, struct formula *lhs, struct formula *rhs) {
    struct formula *f = malloc(sizeof(struct formula));
    f->type = type;
    f->name = name;
    f->lhs = lhs;
    f->rhs = rhs;
    return f;
}

struct formula *
var(const char *name) {
    return mk_formula(VAR, name, NULL, NULL);
}

struct formula *
conj(struct formula *lhs, struct formula *rhs) {
    return mk_formula(CONJ, NULL, lhs, rhs);
}

struct formula *
disj(struct formula *lhs, struct formula *rhs) {
    return mk_formula(DISJ, NULL, lhs, rhs);
}

struct formula *
impl(struct formula *lhs, struct formula *rhs) {
    return mk_formula(IMPL, NULL, lhs, rhs);
}

struct formula *
neg(struct formula *rhs) {
    return mk_formula(NEG, NULL, NULL, rhs);
}

struct formula *
absr(void) {
    return mk_formula(ABSR, NULL, NULL, NULL);
}

int
formula_eq(struct formula *a, struct formula *b) {
    if (a == NULL && b == NULL) {
        return 1;
    }
    if (a == NULL || b == NULL) {
        return 0;
    }
    if (a->type != b->type) {
        return 0;
    }
    if (a->type == ABSR) {
        return 1;
    }
    if (a->type == VAR && !strcmp(a->name, b->name)) {
        return 1;
    }
    if (a->type == CONJ || a->type == DISJ || a->type == IMPL) {
        return formula_eq(a->lhs, b->lhs) && formula_eq(a->rhs, b->rhs);
    }
    if (a->type == NEG) {
        return formula_eq(a->rhs, b->rhs);
    }
    return 0;
}

struct formula *
formula_clone(struct formula *f) {
    if (f == NULL) {
        return NULL;
    }
    return mk_formula(
        f->type, f->name, formula_clone(f->lhs), formula_clone(f->rhs)
    );
}

void
formula_fprint(FILE *f, struct formula *a) {
    if (a == NULL) {
        fprintf(f, "(null)");
    } else if (a->type == VAR) {
        fprintf(f, "%s", a->name);
    } else if (a->type == CONJ || a->type == DISJ || a->type == IMPL) {
        fprintf(f, "(");
        formula_fprint(f, a->lhs);
        if (a->type == CONJ) {
            fprintf(f, " /\\ ");
        } else if (a->type == DISJ) {
            fprintf(f, " \\/ ");
        } else if (a->type == IMPL) {
            fprintf(f, " -> ");
        }
        formula_fprint(f, a->rhs);
        fprintf(f, ")");
    } else if (a->type == NEG) {
        fprintf(f, "!(");
        formula_fprint(f, a->rhs);
        fprintf(f, ")");
    } else if (a->type == ABSR) {
        fprintf(f, "_|_");
    }
}