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137 lines
3.1 KiB
C
137 lines
3.1 KiB
C
/*
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* unparse.c - Dump an expression tree into a string
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*
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* Written 2009, 2012 by Werner Almesberger
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* Copyright 2009, 2012 by Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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/*
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* This is crazily inefficient but who cares :-)
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include "util.h"
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#include "expr.h"
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#include "unparse.h"
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enum prec {
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prec_add,
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prec_mult,
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prec_unary,
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prec_primary,
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};
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static int precedence(op_type op)
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{
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if (op == op_add || op == op_sub)
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return prec_add;
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if (op == op_mult || op == op_div)
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return prec_mult;
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if (op == op_minus)
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return prec_unary;
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if (op == op_num || op == op_string || op == op_var ||
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op == op_sin || op == op_cos || op == op_sqrt || op == op_floor)
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return prec_primary;
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abort();
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}
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static char *merge3(char *a, const char *op, char *b)
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{
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char *buf;
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buf = alloc_size(strlen(op)+strlen(a)+strlen(b)+1);
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sprintf(buf, "%s%s%s", a, op, b);
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free(a);
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free(b);
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return buf;
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}
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static char *merge2(const char *op, char *a)
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{
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char *buf;
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buf = alloc_size(strlen(op)+strlen(a)+1);
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sprintf(buf, "%s%s", op, a);
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free(a);
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return buf;
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}
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static char *unparse_op(const struct expr *expr, enum prec prec);
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static char *unparse_fn(const char *name, const struct expr *expr)
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{
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char *buf, *tmp;
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tmp = unparse_op(expr->u.op.a, prec_add);
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buf = alloc_size(strlen(name)+strlen(tmp)+3);
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sprintf(buf, "%s(%s)", name, tmp);
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free(tmp);
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return buf;
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}
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static char *unparse_op(const struct expr *expr, enum prec prec)
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{
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char tmp[100];
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char *buf, *temp;
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if (prec > precedence(expr->op)) {
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temp = unparse_op(expr, prec_add);
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buf = alloc_size(strlen(temp)+3);
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sprintf(buf, "(%s)", temp);
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free(temp);
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return buf;
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}
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if (expr->op == op_num) {
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snprintf(tmp, sizeof(tmp), "%lg%s",
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expr->u.num.n, str_unit(expr->u.num));
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return stralloc(tmp);
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}
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if (expr->op == op_string)
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return stralloc_printf("\"%s\"", expr->u.str);
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if (expr->op == op_var)
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return stralloc(expr->u.var);
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if (expr->op == op_minus)
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return merge2("-", unparse_op(expr->u.op.a, prec_unary));
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if (expr->op == op_add)
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return merge3(unparse_op(expr->u.op.a, prec_add), "+",
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unparse_op(expr->u.op.b, prec_add));
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if (expr->op == op_sub)
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return merge3(unparse_op(expr->u.op.a, prec_add), "-",
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unparse_op(expr->u.op.b, prec_mult));
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if (expr->op == op_mult)
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return merge3(unparse_op(expr->u.op.a, prec_mult), "*",
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unparse_op(expr->u.op.b, prec_mult));
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if (expr->op == op_div)
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return merge3(unparse_op(expr->u.op.a, prec_mult), "/",
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unparse_op(expr->u.op.b, prec_primary));
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if (expr->op == op_sin)
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return unparse_fn("sin", expr);
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if (expr->op == op_cos)
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return unparse_fn("cos", expr);
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if (expr->op == op_sqrt)
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return unparse_fn("sqrt", expr);
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if (expr->op == op_floor)
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return unparse_fn("floor", expr);
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abort();
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}
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char *unparse(const struct expr *expr)
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{
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return expr ? unparse_op(expr, prec_add) : stralloc("");
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}
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