function to assigning index in front

This is a discussion on function to assigning index in front within the C Programming forums, part of the General Programming Boards category; i am getting in trouble which to write a function to assign or delete the extra index in my loop~ ...

  1. #1
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    function to assigning index in front

    i am getting in trouble which to write a function to assign or delete the extra index in my loop~

    Code:
    #include<stdio.h>
    #include<string.h>
    #include<math.h>
    #include<stdlib.h>
    
    int main()
    {
    	char txt[200];
    	char temp[50][50];
    	char opt[200];
    	float num[200];
    	int i=0, j=0, k=0, n=0, m=0;
    	
    	printf("?\n");
    	gets(txt);
    	
    	i = strlen(txt);
    	
    	for(j=0;j<i;j++)
    	{
    		if(!(txt[j]=='+' || txt[j]=='-' || txt[j]=='*' || txt[j]=='/'))
    		{
    			 temp[m][k] = txt[j]; k++;
    		}
    		else
    		{			
                opt[n] = txt[j]; n++;
    			num[m] = atof(temp[m]); m++;
    			k=0;
                			
    		}
    	}
    	num[m] = atof(temp[m]); m++;
    	
    {
    	int yee = 0;
    	float ans = 0;
    	float tempnum[200]; 
    	int asd = 0;
    	
    	asd = strlen(opt);
    	
    	for(j=0;j<asd;j++)
    	{
    		if(opt[j]=='*')
    		{
    			num[j+1] = num[j] * num[j+1];
    			num[j] = num[j+1];
                ans = num[j+1];          			
    		}
    		if(opt[j]=='/')
    		{
    			num[j+1] = num[j] / num[j+1];
    			num[j] = num[j+1];
                ans = num[j+1];			
    		}
    	}
    	
    	
    	
    	
    	for(j=0;j<asd;j++)
    	{
    		if(opt[j]=='+')
    		{ 
                if(j==0)
                {ans = ans + num[j];}
                else
                {ans = ans + num[j+1];}                   			
    		}
    		if(opt[j]=='-')
    		{
                if(j==0)
                {ans = ans - num[j];}
                else
                {ans = ans - num[j+1];}         			
    		}
    	}
    	
        
        	
    
    	printf("%f",ans);
    }
    	getchar();
    }
    tis is my code n my idea is as folo~

    num = {1, 2, 3, 4}
    opt = "+*+"

    num = {1, 6, 4}
    opt = "++"

    num = {7, 4}
    opt = "+"

    so how can i delete the extra index or assign the index in front? please help me~~

  2. #2
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    You want to get rid of the end of string char at the end of "txt" array?

    As you can see, I'm unclear what you want to do. You can't "get rid of an extra index", since indeces are built into the array, (via pointer design), and can't be removed from it.

  3. #3
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    ok~ let me show you~
    example my expression is 1+2*3+4
    first i save all numbers in num
    num = 1 2 3 4

    then when i found the operator is *,it wil perform num[1] multiply num[2],the the index bcome as below..
    num = 1 6 6 4

    then is + operator, it wil perform num[0]+num[1], the index now bcome as follow.. as you can see, there is repetation of same answer in different index,
    num = 7 7 6 4

    last it wil perform num[3]+num[4],the problem is same as the above, there is repetation too..
    7 7 10 10

    so i hope to delete the extra answer of index~how should i do that?

  4. #4
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    Code:
    for(j=0;j<asd;j++)
    	if(opt[j]=='*')
    		{
    			num[j+1] = num[j] + num[j+1];
    			num[j] = num[j+1];
                ans = num[j+1];          			
    		}
    		if(opt[j]=='/')
    		{
    			num[j+1] = num[j] - num[j+1];
    			num[j] = num[j+1];
                ans = num[j+1];			
    		}
    	}
    sorry~ there are correction for the + and - operation
    this should be the loop for it

  5. #5
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    When you reduce a binary expression like 2 * 3, into one number (6 in this case), then you need to move the higher index numbers (all of them from that point on), of the array, down one index, and "cover up" the extra 6.

    Make sense?

  6. #6
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    yup.. thats the idea.. but how to write it in a function so that i can call it in every mathematical expression?

  7. #7
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    Last edited by Bayint Naung; 08-31-2010 at 07:27 PM.

  8. #8
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    So in your code:
    Code:
    for(j=0;j<asd;j++)
       if(opt[j]=='*')
       {
    	num[j+1] = num[j] + num[j+1];
    	num[j] = num[j+1];
            ans = num[j+1];          			
            /* boogie everything above j, one element to the left */
            for(k=j; num[k]<asd-1;k++)
               num[k] = num[k+1];
       }
       if(opt[j]=='/')
       {
          num[j+1] = num[j] - num[j+1];
          num[j] = num[j+1];
          ans = num[j+1];			
       }
    }
    making the "boogie" code into it's own function and then just calling it, seems good, as does using flags to set if it's needed, and then having the code outside all the if() statements.

    Code:
    int boogie=0;
    
    if(opt[j]=='*') {
      //other code here
      boogie=1;
    }
    if(opt[j]=='/') {
      //other code here
      boogie=1;
    }
    
    /*other if statements here, with their own code 
    setting boogie to 1, if an operator is present, and 
    a reduction is made in the expression. Then:
    */
    if(boogie)  {
       /* boogie everything above j, one element to the left */
       for(k=j; num[k]<asd-1;k++)
          num[k] = num[k+1];
       boogie=0;  /* reset for the next loop */
    }

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