Thread: Problem with isdigit()

I am writing a spell checker.. I have already written it to ignore words that are ALL CAPS.

Code:

int allupper(char* word)
{
    int i = 0;
    
    while(word[i] != NULL)
    {
        if(isupper(word[i]) == 1)
            i++;
        else
            return 0;
    }
    return 1;
}

This worked fine, thought I could do the same thing with isdigit() to have it ignore numbers, but couldn't get it to work...

Code:

int isnumber(char* word)
{
    int i = 0;
    
    while(word[i] != NULL)
    {
        if(isdigit(word[i]) == 1)
            i++;
        else
            return 0;
    }

    printf("Return 1\n");
    return 1;
}

Can anyone tell me what's wrong? Also, is there a way to loop through the string using the Null Terminator as an ending point, I tried while(strcmp("\0", word[i]) != 0) but didn't work right.

Why do you think something is wrong with it?

It seems like it should work, but it won't even recognize word[0] as a digit even if it is, let alone the rest. I don't know why.

This code:

Code:

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

int isnumber(char* word)
{
    int i = 0;

    while(word[i] != '\0')
    {
        if(isdigit(word[i]) == 1)
            i++;
        else {
            printf("word[&#37;d] gives %d.\n", i, isdigit(word[i]));
            return 0;
        }
    }

    printf("Return 1\n");
    return 1;
}

int main(void) {
    char foo[] = "15";
    int bar = isnumber(foo);
    printf("bar is %d.\n", bar);
    return 0;
}

prints

Code:

word[0] gives 4.
bar is 0.

on my (Win32) system. I'm guessing you should reexamine your idea of "true" in C.

Thanks, I remember reading it returns non-zero, didn't know it returns 48-57 for digits 0-9 respectively, set it to != 0 and I was on my way!