/* the following functions convert a string to the specified type, returning 
   true for success and false for failure. These functions differ from the
   strtod and strtol functions in two ways:
   1) they do not recognize any variation of nan as a number, hence it is safe 
      to use these functions to test whether a string is a real string,
      like "Nancy", or a number
   2) they return an error if the trailing characters in the string are not
      numeric. For example, 3x will be treated as a non-numeric string.
*/
extern int string_to_int(char *str, int *return_value);
extern int string_to_long(char *str, long *return_value);
extern int string_to_float(char *str, float *return_value);
extern int string_to_double(char *str, double *return_value);