/*
 * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
 * Released under the terms of the GNU GPL v2.0.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define LKC_DIRECT_LINK
#include "lkc.h"

#define DEBUG_EXPR	0

struct expr *expr_alloc_symbol(struct symbol *sym)
{
    struct expr *e = malloc(sizeof (*e));

    memset(e, 0, sizeof (*e));
    e->type = E_SYMBOL;
    e->left.sym = sym;
    return e;
}

struct expr *expr_alloc_one(enum expr_type type, struct expr *ce)
{
    struct expr *e = malloc(sizeof (*e));

    memset(e, 0, sizeof (*e));
    e->type = type;
    e->left.expr = ce;
    return e;
}

struct expr *expr_alloc_two(enum expr_type type, struct expr *e1,
                            struct expr *e2)
{
    struct expr *e = malloc(sizeof (*e));

    memset(e, 0, sizeof (*e));
    e->type = type;
    e->left.expr = e1;
    e->right.expr = e2;
    return e;
}

struct expr *expr_alloc_comp(enum expr_type type, struct symbol *s1,
                             struct symbol *s2)
{
    struct expr *e = malloc(sizeof (*e));

    memset(e, 0, sizeof (*e));
    e->type = type;
    e->left.sym = s1;
    e->right.sym = s2;
    return e;
}

struct expr *expr_alloc_and(struct expr *e1, struct expr *e2)
{
    if (!e1)
        return e2;
    return e2 ? expr_alloc_two(E_AND, e1, e2) : e1;
}

struct expr *expr_alloc_or(struct expr *e1, struct expr *e2)
{
    if (!e1)
        return e2;
    return e2 ? expr_alloc_two(E_OR, e1, e2) : e1;
}

struct expr *expr_copy(struct expr *org)
{
    struct expr *e;

    if (!org)
        return NULL;

    e = malloc(sizeof (*org));
    memcpy(e, org, sizeof (*org));
    switch (org->type) {
    case E_SYMBOL:
        e->left = org->left;
        break;
    case E_NOT:
        e->left.expr = expr_copy(org->left.expr);
        break;
    case E_EQUAL:
    case E_UNEQUAL:
        e->left.sym = org->left.sym;
        e->right.sym = org->right.sym;
        break;
    case E_AND:
    case E_OR:
    case E_LIST:
        e->left.expr = expr_copy(org->left.expr);
        e->right.expr = expr_copy(org->right.expr);
        break;
    default:
        printf("can't copy type %d\n", e->type);
        free(e);
        e = NULL;
        break;
    }

    return e;
}

void expr_free(struct expr *e)
{
    if (!e)
        return;

    switch (e->type) {
    case E_SYMBOL:
        break;
    case E_NOT:
        expr_free(e->left.expr);
        return;
    case E_EQUAL:
    case E_UNEQUAL:
        break;
    case E_OR:
    case E_AND:
        expr_free(e->left.expr);
        expr_free(e->right.expr);
        break;
    default:
        printf("how to free type %d?\n", e->type);
        break;
    }
    free(e);
}

static int trans_count;

#define e1 (*ep1)
#define e2 (*ep2)

static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1,
                                struct expr **ep2)
{
    if (e1->type == type) {
        __expr_eliminate_eq(type, &e1->left.expr, &e2);
        __expr_eliminate_eq(type, &e1->right.expr, &e2);
        return;
    }
    if (e2->type == type) {
        __expr_eliminate_eq(type, &e1, &e2->left.expr);
        __expr_eliminate_eq(type, &e1, &e2->right.expr);
        return;
    }
    if (e1->type == E_SYMBOL && e2->type == E_SYMBOL &&
        e1->left.sym == e2->left.sym &&
        (e1->left.sym == &symbol_yes || e1->left.sym == &symbol_no))
        return;
    if (!expr_eq(e1, e2))
        return;
    trans_count++;
    expr_free(e1);
    expr_free(e2);
    switch (type) {
    case E_OR:
        e1 = expr_alloc_symbol(&symbol_no);
        e2 = expr_alloc_symbol(&symbol_no);
        break;
    case E_AND:
        e1 = expr_alloc_symbol(&symbol_yes);
        e2 = expr_alloc_symbol(&symbol_yes);
        break;
    default:
        ;
    }
}

void expr_eliminate_eq(struct expr **ep1, struct expr **ep2)
{
    if (!e1 || !e2)
        return;
    switch (e1->type) {
    case E_OR:
    case E_AND:
        __expr_eliminate_eq(e1->type, ep1, ep2);
    default:
        ;
    }
    if (e1->type != e2->type)
        switch (e2->type) {
        case E_OR:
        case E_AND:
            __expr_eliminate_eq(e2->type, ep1, ep2);
        default:
            ;
        }
    e1 = expr_eliminate_yn(e1);
    e2 = expr_eliminate_yn(e2);
}

#undef e1
#undef e2

int expr_eq(struct expr *e1, struct expr *e2)
{
    int res, old_count;

    if (e1->type != e2->type)
        return 0;
    switch (e1->type) {
    case E_EQUAL:
    case E_UNEQUAL:
        return e1->left.sym == e2->left.sym && e1->right.sym == e2->right.sym;
    case E_SYMBOL:
        return e1->left.sym == e2->left.sym;
    case E_NOT:
        return expr_eq(e1->left.expr, e2->left.expr);
    case E_AND:
    case E_OR:
        e1 = expr_copy(e1);
        e2 = expr_copy(e2);
        old_count = trans_count;
        expr_eliminate_eq(&e1, &e2);
        res = (e1->type == E_SYMBOL && e2->type == E_SYMBOL &&
               e1->left.sym == e2->left.sym);
        expr_free(e1);
        expr_free(e2);
        trans_count = old_count;
        return res;
    case E_LIST:
    case E_RANGE:
    case E_NONE:
        /*
         * panic 
         */ ;
    }

    if (DEBUG_EXPR) {
        expr_fprint(e1, stdout);
        printf(" = ");
        expr_fprint(e2, stdout);
        printf(" ?\n");
    }

    return 0;
}

struct expr *expr_eliminate_yn(struct expr *e)
{
    struct expr *tmp;

    if (e)
        switch (e->type) {
        case E_AND:
            e->left.expr = expr_eliminate_yn(e->left.expr);
            e->right.expr = expr_eliminate_yn(e->right.expr);
            if (e->left.expr->type == E_SYMBOL) {
                if (e->left.expr->left.sym == &symbol_no) {
                    expr_free(e->left.expr);
                    expr_free(e->right.expr);
                    e->type = E_SYMBOL;
                    e->left.sym = &symbol_no;
                    e->right.expr = NULL;
                    return e;
                } else if (e->left.expr->left.sym == &symbol_yes) {
                    free(e->left.expr);
                    tmp = e->right.expr;
                    *e = *(e->right.expr);
                    free(tmp);
                    return e;
                }
            }
            if (e->right.expr->type == E_SYMBOL) {
                if (e->right.expr->left.sym == &symbol_no) {
                    expr_free(e->left.expr);
                    expr_free(e->right.expr);
                    e->type = E_SYMBOL;
                    e->left.sym = &symbol_no;
                    e->right.expr = NULL;
                    return e;
                } else if (e->right.expr->left.sym == &symbol_yes) {
                    free(e->right.expr);
                    tmp = e->left.expr;
                    *e = *(e->left.expr);
                    free(tmp);
                    return e;
                }
            }
            break;
        case E_OR:
            e->left.expr = expr_eliminate_yn(e->left.expr);
            e->right.expr = expr_eliminate_yn(e->right.expr);
            if (e->left.expr->type == E_SYMBOL) {
                if (e->left.expr->left.sym == &symbol_no) {
                    free(e->left.expr);
                    tmp = e->right.expr;
                    *e = *(e->right.expr);
                    free(tmp);
                    return e;
                } else if (e->left.expr->left.sym == &symbol_yes) {
                    expr_free(e->left.expr);
                    expr_free(e->right.expr);
                    e->type = E_SYMBOL;
                    e->left.sym = &symbol_yes;
                    e->right.expr = NULL;
                    return e;
                }
            }
            if (e->right.expr->type == E_SYMBOL) {
                if (e->right.expr->left.sym == &symbol_no) {
                    free(e->right.expr);
                    tmp = e->left.expr;
                    *e = *(e->left.expr);
                    free(tmp);
                    return e;
                } else if (e->right.expr->left.sym == &symbol_yes) {
                    expr_free(e->left.expr);
                    expr_free(e->right.expr);
                    e->type = E_SYMBOL;
                    e->left.sym = &symbol_yes;
                    e->right.expr = NULL;
                    return e;
                }
            }
            break;
        default:
            ;
        }
    return e;
}

/*
 * bool FOO!=n => FOO
 */
struct expr *expr_trans_bool(struct expr *e)
{
    if (!e)
        return NULL;
    switch (e->type) {
    case E_AND:
    case E_OR:
    case E_NOT:
        e->left.expr = expr_trans_bool(e->left.expr);
        e->right.expr = expr_trans_bool(e->right.expr);
        break;
    case E_UNEQUAL:
        /*
         * FOO!=n -> FOO 
         */
        if (e->left.sym->type == S_TRISTATE) {
            if (e->right.sym == &symbol_no) {
                e->type = E_SYMBOL;
                e->right.sym = NULL;
            }
        }
        break;
    default:
        ;
    }
    return e;
}

/*
 * e1 || e2 -> ?
 */
static struct expr *expr_join_or(struct expr *e1, struct expr *e2)
{
    struct expr *tmp;

    struct symbol *sym1, *sym2;

    if (expr_eq(e1, e2))
        return expr_copy(e1);
    if (e1->type != E_EQUAL && e1->type != E_UNEQUAL && e1->type != E_SYMBOL
        && e1->type != E_NOT)
        return NULL;
    if (e2->type != E_EQUAL && e2->type != E_UNEQUAL && e2->type != E_SYMBOL
        && e2->type != E_NOT)
        return NULL;
    if (e1->type == E_NOT) {
        tmp = e1->left.expr;
        if (tmp->type != E_EQUAL && tmp->type != E_UNEQUAL
            && tmp->type != E_SYMBOL)
            return NULL;
        sym1 = tmp->left.sym;
    } else
        sym1 = e1->left.sym;
    if (e2->type == E_NOT) {
        if (e2->left.expr->type != E_SYMBOL)
            return NULL;
        sym2 = e2->left.expr->left.sym;
    } else
        sym2 = e2->left.sym;
    if (sym1 != sym2)
        return NULL;
    if (sym1->type != S_BOOLEAN && sym1->type != S_TRISTATE)
        return NULL;
    if (sym1->type == S_TRISTATE) {
        if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
            ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_mod) ||
             (e1->right.sym == &symbol_mod && e2->right.sym == &symbol_yes))) {
            /*
             * (a='y') || (a='m') -> (a!='n') 
             */
            return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_no);
        }
        if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
            ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_no) ||
             (e1->right.sym == &symbol_no && e2->right.sym == &symbol_yes))) {
            /*
             * (a='y') || (a='n') -> (a!='m') 
             */
            return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_mod);
        }
        if (e1->type == E_EQUAL && e2->type == E_EQUAL &&
            ((e1->right.sym == &symbol_mod && e2->right.sym == &symbol_no) ||
             (e1->right.sym == &symbol_no && e2->right.sym == &symbol_mod))) {
            /*
             * (a='m') || (a='n') -> (a!='y') 
             */
            return expr_alloc_comp(E_UNEQUAL, sym1, &symbol_yes);
        }
    }
    if (sym1->type == S_BOOLEAN && sym1 == sym2) {
        if ((e1->type == E_NOT && e1->left.expr->type == E_SYMBOL
             && e2->type == E_SYMBOL) || (e2->type == E_NOT
                                          && e2->left.expr->type == E_SYMBOL
                                          && e1->type == E_SYMBOL))
            return expr_alloc_symbol(&symbol_yes);
    }

    if (DEBUG_EXPR) {
        printf("optimize (");
        expr_fprint(e1, stdout);
        printf(") || (");
        expr_fprint(e2, stdout);
        printf(")?\n");
    }
    return NULL;
}

static struct expr *expr_join_and(struct expr *e1, struct expr *e2)
{
    struct expr *tmp;

    struct symbol *sym1, *sym2;

    if (expr_eq(e1, e2))
        return expr_copy(e1);
    if (e1->type != E_EQUAL && e1->type != E_UNEQUAL && e1->type != E_SYMBOL
        && e1->type != E_NOT)
        return NULL;
    if (e2->type != E_EQUAL && e2->type != E_UNEQUAL && e2->type != E_SYMBOL
        && e2->type != E_NOT)
        return NULL;
    if (e1->type == E_NOT) {
        tmp = e1->left.expr;
        if (tmp->type != E_EQUAL && tmp->type != E_UNEQUAL
            && tmp->type != E_SYMBOL)
            return NULL;
        sym1 = tmp->left.sym;
    } else
        sym1 = e1->left.sym;
    if (e2->type == E_NOT) {
        if (e2->left.expr->type != E_SYMBOL)
            return NULL;
        sym2 = e2->left.expr->left.sym;
    } else
        sym2 = e2->left.sym;
    if (sym1 != sym2)
        return NULL;
    if (sym1->type != S_BOOLEAN && sym1->type != S_TRISTATE)
        return NULL;

    if ((e1->type == E_SYMBOL && e2->type == E_EQUAL
         && e2->right.sym == &symbol_yes) || (e2->type == E_SYMBOL
                                              && e1->type == E_EQUAL
                                              && e1->right.sym == &symbol_yes))
        /*
         * (a) && (a='y') -> (a='y') 
         */
        return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);

    if ((e1->type == E_SYMBOL && e2->type == E_UNEQUAL
         && e2->right.sym == &symbol_no) || (e2->type == E_SYMBOL
                                             && e1->type == E_UNEQUAL
                                             && e1->right.sym == &symbol_no))
        /*
         * (a) && (a!='n') -> (a) 
         */
        return expr_alloc_symbol(sym1);

    if ((e1->type == E_SYMBOL && e2->type == E_UNEQUAL
         && e2->right.sym == &symbol_mod) || (e2->type == E_SYMBOL
                                              && e1->type == E_UNEQUAL
                                              && e1->right.sym == &symbol_mod))
        /*
         * (a) && (a!='m') -> (a='y') 
         */
        return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);

    if (sym1->type == S_TRISTATE) {
        if (e1->type == E_EQUAL && e2->type == E_UNEQUAL) {
            /*
             * (a='b') && (a!='c') -> 'b'='c' ? 'n' : a='b' 
             */
            sym2 = e1->right.sym;
            if ((e2->right.sym->flags & SYMBOL_CONST)
                && (sym2->flags & SYMBOL_CONST))
                return sym2 != e2->right.sym ? expr_alloc_comp(E_EQUAL, sym1,
                                                               sym2)
                    : expr_alloc_symbol(&symbol_no);
        }
        if (e1->type == E_UNEQUAL && e2->type == E_EQUAL) {
            /*
             * (a='b') && (a!='c') -> 'b'='c' ? 'n' : a='b' 
             */
            sym2 = e2->right.sym;
            if ((e1->right.sym->flags & SYMBOL_CONST)
                && (sym2->flags & SYMBOL_CONST))
                return sym2 != e1->right.sym ? expr_alloc_comp(E_EQUAL, sym1,
                                                               sym2)
                    : expr_alloc_symbol(&symbol_no);
        }
        if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
            ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_no) ||
             (e1->right.sym == &symbol_no && e2->right.sym == &symbol_yes)))
            /*
             * (a!='y') && (a!='n') -> (a='m') 
             */
            return expr_alloc_comp(E_EQUAL, sym1, &symbol_mod);

        if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
            ((e1->right.sym == &symbol_yes && e2->right.sym == &symbol_mod) ||
             (e1->right.sym == &symbol_mod && e2->right.sym == &symbol_yes)))
            /*
             * (a!='y') && (a!='m') -> (a='n') 
             */
            return expr_alloc_comp(E_EQUAL, sym1, &symbol_no);

        if (e1->type == E_UNEQUAL && e2->type == E_UNEQUAL &&
            ((e1->right.sym == &symbol_mod && e2->right.sym == &symbol_no) ||
             (e1->right.sym == &symbol_no && e2->right.sym == &symbol_mod)))
            /*
             * (a!='m') && (a!='n') -> (a='m') 
             */
            return expr_alloc_comp(E_EQUAL, sym1, &symbol_yes);

        if ((e1->type == E_SYMBOL && e2->type == E_EQUAL
             && e2->right.sym == &symbol_mod) || (e2->type == E_SYMBOL
                                                  && e1->type == E_EQUAL
                                                  && e1->right.sym ==
                                                  &symbol_mod)
            || (e1->type == E_SYMBOL && e2->type == E_UNEQUAL
                && e2->right.sym == &symbol_yes) || (e2->type == E_SYMBOL
                                                     && e1->type == E_UNEQUAL
                                                     && e1->right.sym ==
                                                     &symbol_yes))
            return NULL;
    }

    if (DEBUG_EXPR) {
        printf("optimize (");
        expr_fprint(e1, stdout);
        printf(") && (");
        expr_fprint(e2, stdout);
        printf(")?\n");
    }
    return NULL;
}

static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1,
                                 struct expr **ep2)
{
#define e1 (*ep1)
#define e2 (*ep2)
    struct expr *tmp;

    if (e1->type == type) {
        expr_eliminate_dups1(type, &e1->left.expr, &e2);
        expr_eliminate_dups1(type, &e1->right.expr, &e2);
        return;
    }
    if (e2->type == type) {
        expr_eliminate_dups1(type, &e1, &e2->left.expr);
        expr_eliminate_dups1(type, &e1, &e2->right.expr);
        return;
    }
    if (e1 == e2)
        return;

    switch (e1->type) {
    case E_OR:
    case E_AND:
        expr_eliminate_dups1(e1->type, &e1, &e1);
    default:
        ;
    }

    switch (type) {
    case E_OR:
        tmp = expr_join_or(e1, e2);
        if (tmp) {
            expr_free(e1);
            expr_free(e2);
            e1 = expr_alloc_symbol(&symbol_no);
            e2 = tmp;
            trans_count++;
        }
        break;
    case E_AND:
        tmp = expr_join_and(e1, e2);
        if (tmp) {
            expr_free(e1);
            expr_free(e2);
            e1 = expr_alloc_symbol(&symbol_yes);
            e2 = tmp;
            trans_count++;
        }
        break;
    default:
        ;
    }
#undef e1
#undef e2
}

static void expr_eliminate_dups2(enum expr_type type, struct expr **ep1,
                                 struct expr **ep2)
{
#define e1 (*ep1)
#define e2 (*ep2)
    struct expr *tmp, *tmp1, *tmp2;

    if (e1->type == type) {
        expr_eliminate_dups2(type, &e1->left.expr, &e2);
        expr_eliminate_dups2(type, &e1->right.expr, &e2);
        return;
    }
    if (e2->type == type) {
        expr_eliminate_dups2(type, &e1, &e2->left.expr);
        expr_eliminate_dups2(type, &e1, &e2->right.expr);
    }
    if (e1 == e2)
        return;

    switch (e1->type) {
    case E_OR:
        expr_eliminate_dups2(e1->type, &e1, &e1);
        /*
         * (FOO || BAR) && (!FOO && !BAR) -> n 
         */
        tmp1 = expr_transform(expr_alloc_one(E_NOT, expr_copy(e1)));
        tmp2 = expr_copy(e2);
        tmp = expr_extract_eq_and(&tmp1, &tmp2);
        if (expr_is_yes(tmp1)) {
            expr_free(e1);
            e1 = expr_alloc_symbol(&symbol_no);
            trans_count++;
        }
        expr_free(tmp2);
        expr_free(tmp1);
        expr_free(tmp);
        break;
    case E_AND:
        expr_eliminate_dups2(e1->type, &e1, &e1);
        /*
         * (FOO && BAR) || (!FOO || !BAR) -> y 
         */
        tmp1 = expr_transform(expr_alloc_one(E_NOT, expr_copy(e1)));
        tmp2 = expr_copy(e2);
        tmp = expr_extract_eq_or(&tmp1, &tmp2);
        if (expr_is_no(tmp1)) {
            expr_free(e1);
            e1 = expr_alloc_symbol(&symbol_yes);
            trans_count++;
        }
        expr_free(tmp2);
        expr_free(tmp1);
        expr_free(tmp);
        break;
    default:
        ;
    }
#undef e1
#undef e2
}

struct expr *expr_eliminate_dups(struct expr *e)
{
    int oldcount;

    if (!e)
        return e;

    oldcount = trans_count;
    while (1) {
        trans_count = 0;
        switch (e->type) {
        case E_OR:
        case E_AND:
            expr_eliminate_dups1(e->type, &e, &e);
            expr_eliminate_dups2(e->type, &e, &e);
        default:
            ;
        }
        if (!trans_count)
            break;
        e = expr_eliminate_yn(e);
    }
    trans_count = oldcount;
    return e;
}

struct expr *expr_transform(struct expr *e)
{
    struct expr *tmp;

    if (!e)
        return NULL;
    switch (e->type) {
    case E_EQUAL:
    case E_UNEQUAL:
    case E_SYMBOL:
    case E_LIST:
        break;
    default:
        e->left.expr = expr_transform(e->left.expr);
        e->right.expr = expr_transform(e->right.expr);
    }

    switch (e->type) {
    case E_EQUAL:
        if (e->left.sym->type != S_BOOLEAN)
            break;
        if (e->right.sym == &symbol_no) {
            e->type = E_NOT;
            e->left.expr = expr_alloc_symbol(e->left.sym);
            e->right.sym = NULL;
            break;
        }
        if (e->right.sym == &symbol_mod) {
            printf("boolean symbol %s tested for 'm'? test forced to 'n'\n",
                   e->left.sym->name);
            e->type = E_SYMBOL;
            e->left.sym = &symbol_no;
            e->right.sym = NULL;
            break;
        }
        if (e->right.sym == &symbol_yes) {
            e->type = E_SYMBOL;
            e->right.sym = NULL;
            break;
        }
        break;
    case E_UNEQUAL:
        if (e->left.sym->type != S_BOOLEAN)
            break;
        if (e->right.sym == &symbol_no) {
            e->type = E_SYMBOL;
            e->right.sym = NULL;
            break;
        }
        if (e->right.sym == &symbol_mod) {
            printf("boolean symbol %s tested for 'm'? test forced to 'y'\n",
                   e->left.sym->name);
            e->type = E_SYMBOL;
            e->left.sym = &symbol_yes;
            e->right.sym = NULL;
            break;
        }
        if (e->right.sym == &symbol_yes) {
            e->type = E_NOT;
            e->left.expr = expr_alloc_symbol(e->left.sym);
            e->right.sym = NULL;
            break;
        }
        break;
    case E_NOT:
        switch (e->left.expr->type) {
        case E_NOT:
            /*
             * !!a -> a 
             */
            tmp = e->left.expr->left.expr;
            free(e->left.expr);
            free(e);
            e = tmp;
            e = expr_transform(e);
            break;
        case E_EQUAL:
        case E_UNEQUAL:
            /*
             * !a='x' -> a!='x' 
             */
            tmp = e->left.expr;
            free(e);
            e = tmp;
            e->type = e->type == E_EQUAL ? E_UNEQUAL : E_EQUAL;
            break;
        case E_OR:
            /*
             * !(a || b) -> !a && !b 
             */
            tmp = e->left.expr;
            e->type = E_AND;
            e->right.expr = expr_alloc_one(E_NOT, tmp->right.expr);
            tmp->type = E_NOT;
            tmp->right.expr = NULL;
            e = expr_transform(e);
            break;
        case E_AND:
            /*
             * !(a && b) -> !a || !b 
             */
            tmp = e->left.expr;
            e->type = E_OR;
            e->right.expr = expr_alloc_one(E_NOT, tmp->right.expr);
            tmp->type = E_NOT;
            tmp->right.expr = NULL;
            e = expr_transform(e);
            break;
        case E_SYMBOL:
            if (e->left.expr->left.sym == &symbol_yes) {
                /*
                 * !'y' -> 'n' 
                 */
                tmp = e->left.expr;
                free(e);
                e = tmp;
                e->type = E_SYMBOL;
                e->left.sym = &symbol_no;
                break;
            }
            if (e->left.expr->left.sym == &symbol_mod) {
                /*
                 * !'m' -> 'm' 
                 */
                tmp = e->left.expr;
                free(e);
                e = tmp;
                e->type = E_SYMBOL;
                e->left.sym = &symbol_mod;
                break;
            }
            if (e->left.expr->left.sym == &symbol_no) {
                /*
                 * !'n' -> 'y' 
                 */
                tmp = e->left.expr;
                free(e);
                e = tmp;
                e->type = E_SYMBOL;
                e->left.sym = &symbol_yes;
                break;
            }
            break;
        default:
            ;
        }
        break;
    default:
        ;
    }
    return e;
}

int expr_contains_symbol(struct expr *dep, struct symbol *sym)
{
    if (!dep)
        return 0;

    switch (dep->type) {
    case E_AND:
    case E_OR:
        return expr_contains_symbol(dep->left.expr, sym) ||
            expr_contains_symbol(dep->right.expr, sym);
    case E_SYMBOL:
        return dep->left.sym == sym;
    case E_EQUAL:
    case E_UNEQUAL:
        return dep->left.sym == sym || dep->right.sym == sym;
    case E_NOT:
        return expr_contains_symbol(dep->left.expr, sym);
    default:
        ;
    }
    return 0;
}

bool expr_depends_symbol(struct expr * dep, struct symbol * sym)
{
    if (!dep)
        return false;

    switch (dep->type) {
    case E_AND:
        return expr_depends_symbol(dep->left.expr, sym) ||
            expr_depends_symbol(dep->right.expr, sym);
    case E_SYMBOL:
        return dep->left.sym == sym;
    case E_EQUAL:
        if (dep->left.sym == sym) {
            if (dep->right.sym == &symbol_yes || dep->right.sym == &symbol_mod)
                return true;
        }
        break;
    case E_UNEQUAL:
        if (dep->left.sym == sym) {
            if (dep->right.sym == &symbol_no)
                return true;
        }
        break;
    default:
        ;
    }
    return false;
}

struct expr *expr_extract_eq_and(struct expr **ep1, struct expr **ep2)
{
    struct expr *tmp = NULL;

    expr_extract_eq(E_AND, &tmp, ep1, ep2);
    if (tmp) {
        *ep1 = expr_eliminate_yn(*ep1);
        *ep2 = expr_eliminate_yn(*ep2);
    }
    return tmp;
}

struct expr *expr_extract_eq_or(struct expr **ep1, struct expr **ep2)
{
    struct expr *tmp = NULL;

    expr_extract_eq(E_OR, &tmp, ep1, ep2);
    if (tmp) {
        *ep1 = expr_eliminate_yn(*ep1);
        *ep2 = expr_eliminate_yn(*ep2);
    }
    return tmp;
}

void expr_extract_eq(enum expr_type type, struct expr **ep, struct expr **ep1,
                     struct expr **ep2)
{
#define e1 (*ep1)
#define e2 (*ep2)
    if (e1->type == type) {
        expr_extract_eq(type, ep, &e1->left.expr, &e2);
        expr_extract_eq(type, ep, &e1->right.expr, &e2);
        return;
    }
    if (e2->type == type) {
        expr_extract_eq(type, ep, ep1, &e2->left.expr);
        expr_extract_eq(type, ep, ep1, &e2->right.expr);
        return;
    }
    if (expr_eq(e1, e2)) {
        *ep = *ep ? expr_alloc_two(type, *ep, e1) : e1;
        expr_free(e2);
        if (type == E_AND) {
            e1 = expr_alloc_symbol(&symbol_yes);
            e2 = expr_alloc_symbol(&symbol_yes);
        } else if (type == E_OR) {
            e1 = expr_alloc_symbol(&symbol_no);
            e2 = expr_alloc_symbol(&symbol_no);
        }
    }
#undef e1
#undef e2
}

struct expr *expr_trans_compare(struct expr *e, enum expr_type type,
                                struct symbol *sym)
{
    struct expr *e1, *e2;

    if (!e) {
        e = expr_alloc_symbol(sym);
        if (type == E_UNEQUAL)
            e = expr_alloc_one(E_NOT, e);
        return e;
    }
    switch (e->type) {
    case E_AND:
        e1 = expr_trans_compare(e->left.expr, E_EQUAL, sym);
        e2 = expr_trans_compare(e->right.expr, E_EQUAL, sym);
        if (sym == &symbol_yes)
            e = expr_alloc_two(E_AND, e1, e2);
        if (sym == &symbol_no)
            e = expr_alloc_two(E_OR, e1, e2);
        if (type == E_UNEQUAL)
            e = expr_alloc_one(E_NOT, e);
        return e;
    case E_OR:
        e1 = expr_trans_compare(e->left.expr, E_EQUAL, sym);
        e2 = expr_trans_compare(e->right.expr, E_EQUAL, sym);
        if (sym == &symbol_yes)
            e = expr_alloc_two(E_OR, e1, e2);
        if (sym == &symbol_no)
            e = expr_alloc_two(E_AND, e1, e2);
        if (type == E_UNEQUAL)
            e = expr_alloc_one(E_NOT, e);
        return e;
    case E_NOT:
        return expr_trans_compare(e->left.expr,
                                  type == E_EQUAL ? E_UNEQUAL : E_EQUAL, sym);
    case E_UNEQUAL:
    case E_EQUAL:
        if (type == E_EQUAL) {
            if (sym == &symbol_yes)
                return expr_copy(e);
            if (sym == &symbol_mod)
                return expr_alloc_symbol(&symbol_no);
            if (sym == &symbol_no)
                return expr_alloc_one(E_NOT, expr_copy(e));
        } else {
            if (sym == &symbol_yes)
                return expr_alloc_one(E_NOT, expr_copy(e));
            if (sym == &symbol_mod)
                return expr_alloc_symbol(&symbol_yes);
            if (sym == &symbol_no)
                return expr_copy(e);
        }
        break;
    case E_SYMBOL:
        return expr_alloc_comp(type, e->left.sym, sym);
    case E_LIST:
    case E_RANGE:
    case E_NONE:
        /*
         * panic 
         */ ;
    }
    return NULL;
}

tristate expr_calc_value(struct expr * e)
{
    tristate val1, val2;

    const char *str1, *str2;

    if (!e)
        return yes;

    switch (e->type) {
    case E_SYMBOL:
        sym_calc_value(e->left.sym);
        return e->left.sym->curr.tri;
    case E_AND:
        val1 = expr_calc_value(e->left.expr);
        val2 = expr_calc_value(e->right.expr);
        return EXPR_AND(val1, val2);
    case E_OR:
        val1 = expr_calc_value(e->left.expr);
        val2 = expr_calc_value(e->right.expr);
        return EXPR_OR(val1, val2);
    case E_NOT:
        val1 = expr_calc_value(e->left.expr);
        return EXPR_NOT(val1);
    case E_EQUAL:
        sym_calc_value(e->left.sym);
        sym_calc_value(e->right.sym);
        str1 = sym_get_string_value(e->left.sym);
        str2 = sym_get_string_value(e->right.sym);
        return !strcmp(str1, str2) ? yes : no;
    case E_UNEQUAL:
        sym_calc_value(e->left.sym);
        sym_calc_value(e->right.sym);
        str1 = sym_get_string_value(e->left.sym);
        str2 = sym_get_string_value(e->right.sym);
        return !strcmp(str1, str2) ? no : yes;
    default:
        printf("expr_calc_value: %d?\n", e->type);
        return no;
    }
}

int expr_compare_type(enum expr_type t1, enum expr_type t2)
{
#if 0
    return 1;
#else
    if (t1 == t2)
        return 0;
    switch (t1) {
    case E_EQUAL:
    case E_UNEQUAL:
        if (t2 == E_NOT)
            return 1;
    case E_NOT:
        if (t2 == E_AND)
            return 1;
    case E_AND:
        if (t2 == E_OR)
            return 1;
    case E_OR:
        if (t2 == E_LIST)
            return 1;
    case E_LIST:
        if (t2 == 0)
            return 1;
    default:
        return -1;
    }
    printf("[%dgt%d?]", t1, t2);
    return 0;
#endif
}

void expr_print(struct expr *e,
                void (*fn) (void *, struct symbol *, const char *), void *data,
                int prevtoken)
{
    if (!e) {
        fn(data, NULL, "y");
        return;
    }

    if (expr_compare_type(prevtoken, e->type) > 0)
        fn(data, NULL, "(");
    switch (e->type) {
    case E_SYMBOL:
        if (e->left.sym->name)
            fn(data, e->left.sym, e->left.sym->name);
        else
            fn(data, NULL, "<choice>");
        break;
    case E_NOT:
        fn(data, NULL, "!");
        expr_print(e->left.expr, fn, data, E_NOT);
        break;
    case E_EQUAL:
        if (e->left.sym->name)
            fn(data, e->left.sym, e->left.sym->name);
        else
            fn(data, NULL, "<choice>");
        fn(data, NULL, "=");
        fn(data, e->right.sym, e->right.sym->name);
        break;
    case E_UNEQUAL:
        if (e->left.sym->name)
            fn(data, e->left.sym, e->left.sym->name);
        else
            fn(data, NULL, "<choice>");
        fn(data, NULL, "!=");
        fn(data, e->right.sym, e->right.sym->name);
        break;
    case E_OR:
        expr_print(e->left.expr, fn, data, E_OR);
        fn(data, NULL, " || ");
        expr_print(e->right.expr, fn, data, E_OR);
        break;
    case E_AND:
        expr_print(e->left.expr, fn, data, E_AND);
        fn(data, NULL, " && ");
        expr_print(e->right.expr, fn, data, E_AND);
        break;
    case E_LIST:
        fn(data, e->right.sym, e->right.sym->name);
        if (e->left.expr) {
            fn(data, NULL, " ^ ");
            expr_print(e->left.expr, fn, data, E_LIST);
        }
        break;
    case E_RANGE:
        fn(data, NULL, "[");
        fn(data, e->left.sym, e->left.sym->name);
        fn(data, NULL, " ");
        fn(data, e->right.sym, e->right.sym->name);
        fn(data, NULL, "]");
        break;
    default:
        {
            char buf[32];

            sprintf(buf, "<unknown type %d>", e->type);
            fn(data, NULL, buf);
            break;
        }
    }
    if (expr_compare_type(prevtoken, e->type) > 0)
        fn(data, NULL, ")");
}

static void expr_print_file_helper(void *data, struct symbol *sym,
                                   const char *str)
{
    fwrite(str, strlen(str), 1, data);
}

void expr_fprint(struct expr *e, FILE * out)
{
    expr_print(e, expr_print_file_helper, out, E_NONE);
}

static void expr_print_gstr_helper(void *data, struct symbol *sym,
                                   const char *str)
{
    str_append((struct gstr *)data, str);
    if (sym)
        str_printf((struct gstr *)data, " [=%s]", sym_get_string_value(sym));
}

void expr_gstr_print(struct expr *e, struct gstr *gs)
{
    expr_print(e, expr_print_gstr_helper, gs, E_NONE);
}
