Thread: string caculator

Hello everyone, I started to build a simple calculator week ago (plus, minus, multiplication ,division and brackets) with strings, so I can put a string for example: 1 +48 * (3-5 * (4 +7)).
I have been towards the end, but my program has a problem when I have the first index minus, and I do not know how to consider the brackets.
**the code worked great for equ such as 2*48+45/2...
** I didnt learn pointers yet.
****Thank for helpers

Code:

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


int calc(char str[25]);
int whoisfirst(char str[25]);
int closebrackets(char str[25]);
int openbrackets(char str[25]);
int calcwith(char str[101]);




int main()
{
    char str[25];
    printf("Enter mathematical expression\n");
    gets(str);
    calc(str);
    calcwith(str);
    system("PAUSE");
    return 0;
}


int closebrackets(char str[25])
{
    int i,startbra,endbra,j;
    for(i=0;i<strlen(str);i++)
    {
        for(i=0;i<strlen(str);i++)
        {
            if(str[i]==')')
            {
                endbra=i;
                i=strlen(str)+2;
                for(j=endbra;str[j]!='(';j--)
                {
                }
                startbra=j;
            }
        }
    }
    return endbra;
}


int openbrackets(char str[25])
{
    int i,startbra,endbra,j;
    for(i=0;i<strlen(str);i++)
    {
        for(i=0;i<strlen(str);i++)
        {
            if(str[i]==')')
            {
                endbra=i;
                i=strlen(str)+2;
                for(j=endbra;str[j]!='(';j--)
                {
                }
                startbra=j;
            }
        }
    }
    return startbra;
}


int whoisfirst(char str[25])
{
    int i,index=-1,j;
    
    for(i=0;i<strlen(str);i++)
    {
        if(str[i]=='*' || str[i]=='/')
        {
            index=i;
            i=strlen(str)+2;
        }
    }
    if(index==-1)
    {
        for(i=0;i<strlen(str);i++)
        {
            if(str[i]=='+' || str[i]=='-')
            {
                index=i;
                i=strlen(str)+2;
            }
        }    
    }    
    printf("Founded at %d\n" , index);
    return index;
}


int calc(char str[25])
{
    int i,insograim,sgorsograim,lifnei,j,sum,index,sum1,sum2,startexp=0,endexp,with=-1,finalsum=-1,endbra;
    char before[25],middle[25],after[25],firstnum[25],secondnum[25],between[25],lifney[25],ahrei[25],newstr[25],new2[25];
    for(i=0;i<strlen(str);i++)
    {
        if(str[i]!='(')
        {
            finalsum=1;
        }
    }
    if(finalsum=1)
    {
            index=whoisfirst(str);
            for(i=0;i<25;i++)
            {
                before[i] = 0;
                middle[i] = 0;
                after[i] = 0;
                firstnum[i] = 0;
                secondnum[i] = 0;
                between[i] = 0;
                lifney[i] = 0;
                ahrei[i] = 0;
                newstr[i]=0;
                new2[i] = 0;
            }
            for(i=0;i<strlen(str);i++)
            {
                for(i=index-1;str[i]>='0' && str[i]<='9';i--)
                {
                    startexp=i;
                }
                for(i=index+1;str[i]>='0' && str[i]<='9';i++)
                {
                    endexp=i;
                }
                for(i=startexp;i<=endexp;i++)
                {
                    between[i-startexp]=str[i];
                }
                for(i=0;i<startexp;i++)
                {
                    lifney[i]=str[i];
                }
                for(i=endexp+1;i<strlen(str);i++)
                {
                    ahrei[i-(endexp+1)]=str[i];
                }
            }
    
            for(i=startexp,j=0;i<index;i++,j++)
            {
                firstnum[j]=str[i];
            }
            sum1=atoi(firstnum);    
            for(i=index+1,j=0;str[i]>='0' && str[i]<='9';i++,j++)
            {
                secondnum[j]=str[i];
            }
            sum2=atoi(secondnum);
            switch (str[index])
            {
                case '+':
                    sum=sum1+sum2;
                    break;
            
                case '-':
                    sum=sum1-sum2;
                    break;
    
                case '*':
                    sum=sum1*sum2;
                    break;
            
                case '/':
                    sum=sum1/sum2;
                    break;
            }
            printf("The string is %s\n" , str); 
    
                strcat(new2,lifney);
                itoa(sum,newstr,10);
                strcpy (between, newstr);
                strcat(new2,between);
                strcat(new2,ahrei);
                strcpy(str,new2);
        
            printf("The new string is %s\n" , str);     
            printf("the length is  %d\n" , strlen(str));
             if(str[0]!='-')
             {
                for(i=0;i<strlen(str);i++)
                {
                    if(str[i]=='+'||str[i]=='-'||str[i]=='*'||str[i]=='/')
                    {
                        calc(str);
                    }
                }
             }
            return sum;
        }
}


/*
THIS IS MY PROBLEM
int calcwithbrackets(char str[101])
{
    int i,insograim,sgorsograim,lifnei,j,sum,index,sum1,sum2,startexp=0,endexp,with=-1,finalsum=-1,endbra;
    char before[25],middle[25],after[25],firstnum[25],secondnum[25],between[25],lifney[25],ahrei[25],newstr[25],new2[25];
//The code
        return 0;
}
*/

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