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/*
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 * simple arithmetic expression evaluator
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 *
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 * Copyright (c) 2002 Michael Niedermayer <michaelni@gmx.at>
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 *
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 * This library is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2 of the License, or (at your option) any later version.
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 *
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 * This library is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library; if not, write to the Free Software
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 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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 *
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 */
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 /*
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 * see http://joe.hotchkiss.com/programming/eval/eval.html
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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#ifndef NAN
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  #define NAN 0
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#endif
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#ifndef M_PI
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#define M_PI 3.14159265358979323846
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#endif
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#define STACK_SIZE 100
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typedef struct Parser{
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    double stack[STACK_SIZE];
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    int stack_index;
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    char *s;
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    double *const_value;
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    char **const_name;          // NULL terminated
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    double (**func1)(void *, double a); // NULL terminated
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    char **func1_name;          // NULL terminated
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    double (**func2)(void *, double a, double b); // NULL terminated
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    char **func2_name;          // NULL terminated
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    void *opaque;
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} Parser;
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static void evalExpression(Parser *p);
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static void push(Parser *p, double d){
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    if(p->stack_index+1>= STACK_SIZE){
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        fprintf(stderr, "stack overflow in the parser\n");
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        return;
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    }
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    p->stack[ p->stack_index++ ]= d;
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//printf("push %f\n", d); fflush(stdout);
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}
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static double pop(Parser *p){
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    if(p->stack_index<=0){
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        fprintf(stderr, "stack underflow in the parser\n");
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        return NAN;
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    }
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//printf("pop\n"); fflush(stdout);
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    return p->stack[ --p->stack_index ];
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}
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static int strmatch(char *s, char *prefix){
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    int i;
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    for(i=0; prefix[i]; i++){
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        if(prefix[i] != s[i]) return 0;
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    }
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    return 1;
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}
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static void evalPrimary(Parser *p){
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    double d, d2=NAN;
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    char *next= p->s;
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    int i;
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    /* number */
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    d= strtod(p->s, &next);
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    if(next != p->s){
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        push(p, d);
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        p->s= next;
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        return;
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    }
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    /* named constants */
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    for(i=0; p->const_name[i]; i++){
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        if(strmatch(p->s, p->const_name[i])){
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            push(p, p->const_value[i]);
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            p->s+= strlen(p->const_name[i]);
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            return;
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        }
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    }
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    p->s= strchr(p->s, '(');
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    if(p->s==NULL){
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        fprintf(stderr, "Parser: missing ( in \"%s\"\n", next);
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        return;
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    }
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    p->s++; // "("
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    evalExpression(p);
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    d= pop(p);
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    p->s++; // ")" or ","
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    if(p->s[-1]== ','){
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        evalExpression(p);
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        d2= pop(p);
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        p->s++; // ")"
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    }
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         if( strmatch(next, "sinh"  ) ) d= sinh(d);
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    else if( strmatch(next, "cosh"  ) ) d= cosh(d);
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    else if( strmatch(next, "tanh"  ) ) d= tanh(d);
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    else if( strmatch(next, "sin"   ) ) d= sin(d);
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    else if( strmatch(next, "cos"   ) ) d= cos(d);
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    else if( strmatch(next, "tan"   ) ) d= tan(d);
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    else if( strmatch(next, "exp"   ) ) d= exp(d);
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    else if( strmatch(next, "log"   ) ) d= log(d);
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    else if( strmatch(next, "squish") ) d= 1/(1+exp(4*d));
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    else if( strmatch(next, "gauss" ) ) d= exp(-d*d/2)/sqrt(2*M_PI);
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    else if( strmatch(next, "abs"   ) ) d= abs(d);
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    else if( strmatch(next, "max"   ) ) d= d > d2 ? d : d2;
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    else if( strmatch(next, "min"   ) ) d= d < d2 ? d : d2;
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    else if( strmatch(next, "gt"    ) ) d= d > d2 ? 1.0 : 0.0;
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    else if( strmatch(next, "lt"    ) ) d= d > d2 ? 0.0 : 1.0;
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    else if( strmatch(next, "eq"    ) ) d= d == d2 ? 1.0 : 0.0;
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//    else if( strmatch(next, "l1"    ) ) d= 1 + d2*(d - 1);
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//    else if( strmatch(next, "sq01"  ) ) d= (d >= 0.0 && d <=1.0) ? 1.0 : 0.0;
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    else{
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        int error=1;
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        for(i=0; p->func1_name && p->func1_name[i]; i++){
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            if(strmatch(next, p->func1_name[i])){
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                d= p->func1[i](p->opaque, d);
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                error=0;
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                break;
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            }
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        }
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        for(i=0; p->func2_name && p->func2_name[i]; i++){
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            if(strmatch(next, p->func2_name[i])){
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                d= p->func2[i](p->opaque, d, d2);
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                error=0;
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                break;
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            }
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        }
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        if(error){
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            fprintf(stderr, "Parser: unknown function in \"%s\"\n", next);
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            return;
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        }
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    }
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    if(p->s[-1]!= ')'){
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        fprintf(stderr, "Parser: missing ) in \"%s\"\n", next);
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        return;
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    }
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    push(p, d);
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}      
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static void evalPow(Parser *p){
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    int neg= 0;
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    if(p->s[0]=='+') p->s++;
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    if(p->s[0]=='-'){ 
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        neg= 1;
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        p->s++;
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    }
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    if(p->s[0]=='('){
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        p->s++;;
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        evalExpression(p);
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        if(p->s[0]!=')')
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            fprintf(stderr, "Parser: missing )\n");
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        p->s++;
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    }else{
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        evalPrimary(p);
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    }
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    if(neg) push(p, -pop(p));
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}
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static void evalFactor(Parser *p){
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    evalPow(p);
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    while(p->s[0]=='^'){
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        double d;
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        p->s++;
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        evalPow(p);
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        d= pop(p);
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        push(p, pow(pop(p), d));
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    }
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}
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static void evalTerm(Parser *p){
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    evalFactor(p);
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    while(p->s[0]=='*' || p->s[0]=='/'){
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        int inv= p->s[0]=='/';
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        double d;
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        p->s++;
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        evalFactor(p);
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        d= pop(p);
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        if(inv) d= 1.0/d;
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        push(p, d * pop(p));
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    }
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}
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static void evalExpression(Parser *p){
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    evalTerm(p);
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    while(p->s[0]=='+' || p->s[0]=='-'){
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        int sign= p->s[0]=='-';
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        double d;
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        p->s++;
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        evalTerm(p);
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        d= pop(p);
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        if(sign) d= -d;
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        push(p, d + pop(p));
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    }
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}
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double ff_eval(char *s, double *const_value, char **const_name,
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               double (**func1)(void *, double), char **func1_name, 
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               double (**func2)(void *, double, double), char **func2_name,
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               void *opaque){
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    Parser p;
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    p.stack_index=0;
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    p.s= s;
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    p.const_value= const_value;
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    p.const_name = const_name;
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    p.func1      = func1;
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    p.func1_name = func1_name;
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    p.func2      = func2;
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    p.func2_name = func2_name;
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    p.opaque     = opaque;
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    evalExpression(&p);
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    return pop(&p);
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}