Thread: Checking for a number

So I have a function that is called everytime the user inputs something, to check whether it is a number or, includes letters aswell. But I want the user to be able to input a decimal, such as 1.234 or 0.4354 etc. I also want the user to be able to input negative numbers, and fractions.

Here is my function at the moment,

Code:

int is_digit(char* digit)
    {
         int len=strlen(digit);
         int i;
         for(i=0;i<len;i++)
        {
             if(isdigit(digit[i])==0)
             {
                 if ((digit[i]) == ".")
                 {
                    
                 }
                 else
                 {
                   return -1;
                 }
              }
        }

     return atoi(digit);
    }

It should only be checking to see whether the letter is a decimal point, and if so allow it, but it doesnt work. I am going to also make if statements checking whether the first letter is a - sign and allow that in a similar manner.

Please can someone sport whats wrong.

Thanks

Thanks and what about

Code:

  if ((digit[i]) == '-')//checking whether the first symbol, that is a negative sign
                     {
                     }
                     else
                     {
                         return -1;
                     }

It worked for the decimal, but not for minus sign for some reason?

the full loop is:

Code:

for(i=0;i<len;i++)
        {
             if(isdigit(digit[i])==0)
             {
                 if (i==0)//checking to see whether first character is 0, before checking if its a minus.
                 {
                     if ((digit[i]) == '-')//checking whether the first symbol, that is a negative sign
                     {
                     }
                     else
                     {
                         return -1;
                     }
                 }

                 if ((digit[i]) == '.')//checking whether the symbol that is not a number, is a decimal point.
                 {

                 }
                 else
                 {
                   return -1;
                 }
              }
        }

thanks for your help