char x isdigit ?

[Cero.Uno]

Hi guys,

I'm having trouble with the following function, can anyone spot whats wrong, I can't get atoi to work, the only work around thus far is doing this which I don't particularly like

    if ( isdigit( x ) )
        return (x - 48);

I want to be able to use atoi

int get_coord(char x)
{

    const char cols[10] = "ABCDEFGHIJ";
    int i;

    if ( isdigit( atoi(&x) ) )
        return x;

    for ( i = 0; i < 10; i++ )
    {
        if ( x == cols[i] )
            return i;
    }

}

[Dino]

atoi() works on strings, not single characters.

[Cero.Uno]

compiles ok but errors out.

[Cero.Uno]

atoi() works on strings, not single characters.

Can you recommend any alternative..., would you say

        return (x - 48);

is bad programming practice?

[master5001]

That isn't how one goes about using atoi, first of all.

Example

const char *numstr = "145";

int x = atoi(numstr);

;

And secondly, there is nothing wrong with isdigit() in this case. You just need to use a string, not a pointer to a char. Unless, that char contains 0, the program will likely do things you do not like... And if the char does contain 0, then nothing is done, which you still won't like.

[master5001]

Can you recommend any alternative..., would you say

        return (x - 48);

is bad programming practice?

// how about..

int get_coord(char *x)
{
   if(x && isdigit(*x))
     return atoi(x);
}

[Dino]

What are you trying to do with this function? Are you wanting to verify a value is a proper number? If so, are you really passing a single character to this routine?

[cpjust]

Can you recommend any alternative..., would you say

        return (x - 48);

is bad programming practice?

Yes, very bad. Magic numbers make for write-only code.
Not to mention it isn't portable since it assumes everything uses ASCII.
This is a little better, and should be portable:

return (x - '0');

[Cero.Uno]

What are you trying to do with this function? Are you wanting to verify a value is a proper number? If so, are you really passing a single character to this routine?

returning coordinates, I'm using a matrix for a gridding system for my battleships game. I'm attempting to make the function generic, should the value be B on the display from the users input then I want 1 to be returned from the loop, however should the numbered row ( >> x << ) be a number by the user, I just want the function to return.

[Cero.Uno]

 return (x - '0');

works good.

[master5001]

Shouldn't a coordinate be x and y? Perhaps numbers indicating x and letters indicating y.

[Cero.Uno]

this function is invoked for both inputs OF x and y.

x = get_coord(input[1]);
y = get_coord(input[0]);