Thread: char to double

Hi

Is there anyway to take a number out of a char and use it in a calculation.
Say someone enters a char of form Character#.#
is there a command to take the number out?
for example:
A2.1 -> 2.1
the 2.1 can then be used in a calculation?

you might want to finish the psuedocode first its due before the code

i saw this:
atof (yourString)

but i dunno if that works for my case?

hahaha well that can be done, jus dunno how to use the f1.2 etc in a calculation, do you know wat the formula for exposure time is @juststartedC

Ok so basically:
sscanf(str,"A%lf",&charss); //Do i have to use sscanf or can i use fscanf?
strtod(charss);
printf("your number in char is: %lf",charss);

?

Originally Posted by QuantumPete

You need to work on your terminology. A 'char' is a single ASCII letter: 'A', 'f', '1', '%' are all chars, what you're talking about are 'strings' or 'char arrays'.

QuantumPete
P.S. Please search the forums first before you post, we've covered that topic extensivly with one of your classmates.

ok yea, so what ill use is a char array [4]

Originally Posted by taurus

hahaha well that can be done, jus dunno how to use the f1.2 etc in a calculation, do you know wat the formula for exposure time is @juststartedC

Im not sure. fortunately i have a good friend who is a professional programmer, he will take care of it (wink)

hahahaha, then the exam comes and youll find it hard wink
----------------------------------
hey matsp, so does this look like the programming:

sscanf(str,"A%lf",&charss); //Do i have to use sscanf or can i use fscanf?
strtod(charss);
printf("your number in char is: %lf",charss);

?

Following what dawks said before here is a sample code to understand how to use the strtod function.

Code:

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

//Get a string from input.
char *GetBuffer(int Buf_Size)
{
     char *Buffer = malloc(Buf_Size * sizeof(char));
     if(Buffer == NULL)
               return NULL;
     else
     {
         if(fgets(Buffer, Buf_Size, stdin) == NULL)
         {
                          free(Buffer);
                          return NULL;
         }
         else
         {
             if(Buffer[strlen(Buffer)-1] == '\n')
             {
                                         Buffer[strlen(Buffer)-1] = '\0';
                                         return Buffer;
             }
         }
     }
}
//Use of strtod.
double GetDouble(char *Buffer)
{
       if(Buffer == NULL)
       {
                 printf("NULL Buffer.\n");
                 return 0.0;
       }
       else
       {
           //Variables.
           int i;
           char *endPtr = NULL;
           double retVal = 0.0;
           //Use here.
           for(i = 0; i < strlen(Buffer) && !isdigit(Buffer[i]); i++);
           if(i == strlen(Buffer))
           {
                printf("No number was found to convert from buffer.\n");
                return 0.0;
           }
           else
           {
               //The for loop stops when the first digit is found.
               retVal = strtod(&Buffer[i], &endPtr);
               if(retVal == 0.0)
               {
                    printf("No valid conversion was made.\n");
                    return 0.0;
               }
           else
               return retVal;
           }
       }
}

int main(int argc, char *argv[])
{
  char *Buf = GetBuffer(1024);
  printf("%lf\n", GetDouble(Buf));
  free(Buf);
  system("PAUSE");	
  return 0;
}

Bokarinho.

Originally Posted by dwks

Some notes about Bokarinho's code:

1. system("PAUSE") is unportable and should be avoided if possible.
2. Casting malloc() is a bad idea. I wouldn't if I were you.
3. sizeof(char) is always 1, so you could leave it out if you wanted to.
4. strlen() is expensive (in terms of time) to compute. I'd compute it once, store the result in a variable, and use that rather than using strlen(Buffer) all of the time.
5. //-style comments are C99, though many C89 compilers support them.
6. isdigit() is in <ctype.h>, and you should include it.
7. 
   
   Code:

   double GetDouble(char *Buffer)
   {
          if(Buffer == NULL)
          {
                    printf("NULL Buffer.\n");
                    return 0.0;
          }
          else
          {

   There's no need for the else there. The return statement takes care of that.
8. Your indentation makes it difficult to see which else belongs to which if in GetDouble().
9. 
   
   Code:

   char *GetBuffer(int Buf_Size)

   Buf_Size should perhaps be a size_t.

Thanks for your comments.
1. I will stop casting malloc, its a University habit a teacher always casting malloc in C, still does though i have told him why not.
2. The code i write is in a way very fast and typical, i want to help not to sell a 'perfect project' to someone.
3. About strlen that was something i never had in mind, thanks for the tip, i will use it.
4. Oh my god even the comments bother you??????
5. The else statement goes(it is no harm to use else statements in your code) to help my mind work better and never forget the previous code, but if there is wrong with that i will stop it too.
6. On closer look i mispeled your name i am curious how you couldnt see that too.......
7. I am not an advanced C programmer, i want to state that, i have some C knowledge i want to help other people solve their problems.

However, thanks for the comments i always learn from my mistakes.