Thread: Strtok() - int or float it be?

I think you will have to do something like:

if (strchr(str,'.')) {

to decide.

Nope. strchr takes a const char *, so it cannot change the passed string.

Yeah, if there's no "." it returns NULL. This is a "truth test":

Code:

if (strchr(str,'.'))

means:

Code:

if (strchr(str,'.') != NULL)

The opposite:

Code:

if (!strchr(str,'.')) 
// means:
if (strchr(str,'.') == NULL)

Because you don't care where it is, just whether it is there. Or not.

Originally Posted by towed

My question is: is their a way to know or test to see if str will be a int or a float?

Many ints will also be floats. I would choose to use strtol and strtof to attempt conversion of the text. If either is successful, you know what you got. If neither is successful, odds are it was neither. The order of calling these two allows you to have preference for one or the other. Something like this:

Code:

#include <stdio.h>
#include <stdlib.h>

union uType
{
   int   i;
   float f;
};

struct tType
{
   enum eType
   {
      TYPE_INT, TYPE_FLOAT, TYPE_OTHER, TYPE_TOTAL
   } type;
   union uType value;
};

int foo(struct tType *data, const char *text)
{
   char *end;
   data->value.i = strtol(text, &end, 10);
   if ( end > text && *end == '\0' )
   {
      data->type = TYPE_INT;
      return 1;
   }
   data->value.f = strtof(text, &end);
   if ( end > text && *end == '\0' )
   {
      data->type = TYPE_FLOAT;
      return 1;
   }
   data->type = TYPE_OTHER;
   return 0;
}

int main() 
{
   const char *input[] =
   {
      "",
      "-123",
      "-123.45",
      "123E-2",
      "123abc",
      "xyz",
      "123E2",
      "1.23.E2",
   };
   size_t i;
   for ( i = 0; i < sizeof input / sizeof *input; ++i )
   {
      struct tType data;
      int result = foo(&data, input[i]);
      printf("\"%s\" : ", input[i]);
      switch ( data.type )
      {
      case TYPE_INT:   printf("TYPE_INT   %d", data.value.i); break;
      case TYPE_FLOAT: printf("TYPE_FLOAT %g", data.value.f); break;
      default:         fputs("TYPE_OTHER", stdout); break;
      }
      putchar('\n');
   }
   return 0;
}

/* my output
"" : TYPE_OTHER
"-123" : TYPE_INT   -123
"-123.45" : TYPE_FLOAT -123.45
"123E-2" : TYPE_FLOAT 1.23
"123abc" : TYPE_OTHER
"xyz" : TYPE_OTHER
"123E2" : TYPE_FLOAT 12300
"1.23.E2" : TYPE_OTHER
*/

Good one.

I would just check for the dot and then sscanf one way or the other tho -- if that fails: NAN. Who cares about those fancy smancy scientific numbers or whatever they are called.

Originally Posted by towed

Code:

str = strtok(line, ",");

Is what I use, but I encountered a situation where there is an variable pass the last ","
i.e.
Line 1: 3.1, 2, 1
Line 2: 3, 14.25, 131

How can the last variable be read from Line 1 since it has no token to search?

I immediately looked at strtok(line, " ") and strtok(line, "\n") but got an compiler error (NULL is returned).

Code:

strtok(line, " ,\n");

will break on a space, a comma, or a newline, this might work depending on if your line retains the newline or not. fgets does retain the newline.

Using strchr to differentiate a float from a int is hackish, IMO. Any parseable int is also a parsable float, so I'd use strtod (or equivalent) to parse floats.