Checking if *char is whitespace or characters C++

Question

I was trying to discard invalid values, ie whitespaces and characters as I want to only parse double values.

My .txt file looks like this...

1.45-1.46
    -1.56
1.78-dead
-abc
1.34-2.45
1.56-9.01

Basically, I only want to store valid doubles, so the first line 1.45-1.46 , the fifth line 1.34-2.45 and the last line 1.56-9.01 are valid and the rest are invalid.

I have written some code, however it does not recognize the whitespace or characters . I am getting a ISO C++ forbids comparison between pointer and integer error.

This is the code

  char **marks;
  marks = new char*[7]
  for(int i=0; i<7; i++)
  {
    marks[i] = new char[64];
    istreams.getline(marks[i], 64);
    char *delims;
    delims = strtok (marks[i]," -");
    while (delims != NULL)
    {
      if(delims == '') // DOES NOT LIKE THIS, I WANT IT TO CHECK FOR WHITESPACE AND ALPHA CHARACTERS LIKE 'A', 'B', 'C'...
      {
         cout << "Invalid double" << endl;
      }
      else
      {
        cout << atof(delims);
        delims = strtok (NULL, " ,.-");
      }
    }
  }

Answer 1

Check out the functions

isalpha(int)
isspace(int)

You'll need to check each char individually by casting it to an int, though:

bool containsWhitespace(char const * c) {
    char temp = *c;
    if(temp != '\0') {
        if( isspace(temp) )
           return true;
    } else {
        return false;
    }
    return containsWhitespace(++c);
}

int main() {
    if(containsWhitespace("ThisIsATest")) printf("First test failed.");
    if(!containsWhitespace("This is a test")) printf("Second test failed.");
}

http://www.cplusplus.com/reference/cctype/isalpha/

http://www.cplusplus.com/reference/cctype/isspace/