Thread: while loops...a problem with my simple code?

I think there may be a problem with my usage of brackets below.
Any ideas on this simple program to find roots of quadratic equation?

many thanks!

include

Code:

#include <stdio.h> 
#include <stdlib.h> 
#include <math.h> 
int main()

{
char answer;
int a,b,c;
float single_root, root_part1, root_part2;//declaring function variables these 
                                          //being different elements of the 
                                          //quadratic formula
float root1, root2;
int is_complex;

do

printf("Enter coeficients a b c: ");
scanf("&#37;f %f %f", &a, &b, &c);

is_complex = 0;   //(is_complex) function = 0 if a=0
   
   if (a==0)
   {
   single_root=-1.0*c/b;//stating variables
   }
   
   else
   
   {
   root_part1 = -1.0*b/(2.0*a); //stating variables
   root_part2= b*b-4.0*a*c;
   
      if (root_part2<0.0)
      {
                         
      is_complex = 1; 
      
      root_part2= -1.0*root_part2;//remember this is not equal to, 
                                  //this is a directive
      }
      
            
       root_part2=sqrt(root_part2)/(2.0*a);
            
       }
            
        if(a==0.0)
            
       {
        Printf("single_root = %f\n ", single_root);//single root case
       }
            
        else if  (is_complex==1)
               
       {
       printf("root 1 = %.2f+%.2f i\n", root_part1, root_part2); 
       printf("root 1 = %.2f-%.2f i\n", root_part1, root_part2);
       }
               
       else 
               
       {
       root1= root_part1+root_part2;  
       root2= root_part1-root_part2;
               
   printf("root1 = %.2f", root1);
   printf("root2 = %.2f", root2);
   }
               
   {
   printf("enter next set of coefficients (y/n): ");
   scanf(" %c", &answer);
   }

           
   while (answer != 'n' && answer != 'N'); 
           
   scanf("d\n");   
   exit(0);
   
}

C is case sensitive. "printf" is not the same thing as "Printf". Only "printf" works. (Nearly all standard library functions and identifiers are in lowercase, except things like _Bool.)

Code:

while (answer != 'n' && answer != 'N');

Consider tolower() or toupper() from <ctype.h>.

As an optional suggestion, indenting a little bit better will not hurt. http://cpwiki.sf.net/User:Elysia/Identation
It will make the code easier to read and make it easier to spot bugs as well (or avoiding them)!

I'm actually wondering if it was all on one line or something . . . .

Last edited by Dave_Sinkula : Today at 12:04 PM. Reason: My eyes tire of the wide view.

This, of course, does nothing useful:

Code:

scanf("d\n");

Originally Posted by dwks

Code:

scanf("d\n");

Not only does it _NOT_ do anything useful, but it's quite possibly going to cause a crash on a modern system, as it takes the next word down on the stack as an address to write an integer value to. If this address is for example the return address or the frame-pointer, it will lead to very bad things. If it's "only" a local variable [and this contains a valid memory address], you'll have strange results. In short, very strange things could happen here, and very few of the potential scenarios are on the good side of "nothing".

--
Mats

So what compiler do you use?

Originally Posted by matsp

Not only does it _NOT_ do anything useful, but it's quite possibly going to cause a crash on a modern system, as it takes the next word down on the stack as an address to write an integer value to. If this address is for example the return address or the frame-pointer, it will lead to very bad things. If it's "only" a local variable [and this contains a valid memory address], you'll have strange results. In short, very strange things could happen here, and very few of the potential scenarios are on the good side of "nothing".

--
Mats

You may not have noticed that there is no %; it's just "d\n". As far as I can tell, it requires the user to enter "d" before continuing.

Note to OP: /n is not the same thing as \n.

A better way would be to use getchar() instead More portable.

Also see cpwiki.sf.net/Pause_console