ValidateAlphaNumerice values

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September 13th, 2012, 11:00 AM

r15

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ValidateAlphaNumerice values

Hi There,
I have to validate the Alphanumeric values as below, please correct me if Iam wrong.
The valid values are:
' ' (one space)
1
2
3
4
I have written the below code, please help

int isValid(char c)
int rc = 0;
{
if(c == ' ' || c == '1' || c == '2' || c == '3' || c == '4')
rc = 0;
else
rc = 1;
return (rc) ;
}

September 13th, 2012, 11:05 AM

bdb

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You need to put the definition of rc inside the braces

Code:

int isValid(char c)
{
    int rc = 0;

    if(c == ' ' || c == '1' || c == '2' || c == '3' || c == '4')
        rc = 0;
    else
        rc = 1;
    return (rc) ;
}

Also the parenthesis around the value to be returned are usually not used (but they are merely redundant).
A plain return rc; would have been enough.

September 13th, 2012, 11:45 AM

b49P23TIvg

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I don't believe in extra code....

Code:

#define ISVALID(C) (!(C == ' ' || C == '1' || C == '2' || C == '3' || C == '4'))

int isValid(char c) {
  return !(c == ' ' || c == '1' || c == '2' || c == '3' || c == '4');
}

(sure, we could use unequal to this and unequal to that...)

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September 13th, 2012, 12:43 PM

bdb

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I'm pretty sure both the long and the short version compile to the same object code (possibly after turning on some level of optimization) ... checking ... HMMM ... well almost: the difference is very very small

September 13th, 2012, 08:46 PM

Lux Perpetua

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Quote:

Originally Posted by b49P23TIvg

I don't believe in extra code....

Code:

#define ISVALID(C) (!(C == ' ' || C == '1' || C == '2' || C == '3' || C == '4'))

int isValid(char c) {
  return !(c == ' ' || c == '1' || c == '2' || c == '3' || c == '4');
}

(sure, we could use unequal to this and unequal to that...)

Your macro is problematic:

1. If C is an expression with side effects (like `getchar()'), those effects will occur five times - certainly a bug.
2. Due to operator precedence, if C is e.g. `x ^ 0x1', the macro breaks.

Point 2 can be fixed by parenthesizing all occurences of C in the macro definition, but it's difficult to fix point 1 without introducing other problems. I would actually advise C programmers not to use macros at all. If you just want to avoid the overhead of a function call, use an inline function instead (supported by both C99 and C++).

Comments on this post

b49P23TIvg agrees: I swear I've never before forgotten to parenthesize macro arguments!

ValidateAlphaNumerice values

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