pset2 how to use ctype.h functions

Question

it takes me really long time to figure this out and am not making any progress so i was wondering if someone could help.

how do i use, for example, isalpha in if statement. like:

    if ( argc != 2 || isalpha(argv[1])
{
return 1;
}

what i want is to isalpha check if argv[1] are characters and not numbers and if its not characters i want to make return 1; go through. writing it like this:

  string key = argv[1]; 
   if (argc != 2 || isalpha(key)
  { 
    return 1; 
  }

is not helping. now typing ! before isalpha is not helping either. is it possible to use isalpha and other similiar functions(isdigit) like this or not? thanks

Answer 1

isalpha() takes a single character. When you try to jam a complete string down its throat, it chokes and coughs up a seg fault. You need to loop through the string and test each char individually.

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Answer 2

for (int i = 0, j = strlen(key); i < j; i ++)

    {
         if (!isalpha(key[i]))
        return 1;
    }

ok, it works like this. thank you