Numeric Checking in C++

I'm looking for something along the guidelines of IsNumeric() in VB for C++. Yeah, I'm a vb programmer https://www.sharkyforums.com/images/.../2005/06/6.gif

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EDIT: don't know (sorry)

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Keep it brief

[This message has been edited by dighn (edited January 20, 2002).]

Quote:

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Originally posted by Raptor2150:
I'm looking for something along the guidelines of IsNumeric() in VB for C++. Yeah, I'm a vb programmer https://www.sharkyforums.com/images/.../2005/06/6.gif

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What is it that you are trying to accomplish? We might be able to code somethin' for ya.



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I only chewed in self-defense.

Wow, is it really that difficult in c? I just wanted to check if an inputted variable of type float was actually a numeric value before I tried to do any calculations...

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well u could alwasy write one yourself...

this code will make sure the string is in the format -x.x where - . are optional and x can be any number of digits as long as it's at least 1 digit. this is just sort of a demo so there's lots of room for improvement

Code:

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bool isNumeric(const char* s)
{
  bool needDigit = true;
  bool gotDecimal = false;

  for(int i = 0; i < strlen(s);i++)
  {
    if(s[i] < '0' | | s[i] > '9')
    {
      if(s[i] == '-')
      {
                if(i != 0)
          return false;
      }
      else if(s[i] == '.')
      {
                if(needDigit)
          return false;
        if(gotDecimal)
          return false;
        needDigit = true;
        gotDecimal = true;
      }
      else
        return false;
    }
        else
                needDigit = false;
  }
  return !needDigit;
}

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Keep it brief

Quote:

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Originally posted by Raptor2150:
I'm looking for something along the guidelines of IsNumeric() in VB for C++. Yeah, I'm a vb programmer https://www.sharkyforums.com/images/.../2005/06/6.gif

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The easiest way is to convert the string to a number using scanf:

Code:

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char buffer[256] = "-10";
int num;
sscanf(buffer, "%d", &num);

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The trick is that scanf will return the number of arguments that it successfully assigned. Thus:

Code:

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if( sscanf(buffer, "%d", &num) != 1 ) {
  /* error here */
}

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Wow, is it really that complicated? I would think that there would be some sort of function for it. Anyways, thanks all.

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Athlon XP 1800+ (OC pending)
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256mb Crucial pc2100 ddr
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ATI Radeon8500 (300/300)
Antec PP403x 400w

Yep, C(++) doesn't always provide every little thing that people may want. But, that's why you make your own functions, then it is no longer complicated. ... as long as you have good comments. https://www.sharkyforums.com/images/.../2005/06/5.gif

Uh, if(!isalpha(stuff)), or is that only PHP or something?

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Quote:

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Originally posted by schnarf283:
Uh, if(!isalpha(stuff)), or is that only PHP or something?

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Sure, you can use isdigit(...), however that doesn't really handle negative numbers properly. There are regular expression libraries, but these are cumbersome.

so:

Code:

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/* returns non-zero if true */
int isAsciiInteger(char *nzstr)
{
  int dummy;
  return(sscanf(nzstr, "%d", &dummy) == 1);
}

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