strcspn() stopping at a period - c

Question

I'm writing a function that should parse a string containing a description of a dice roll, for instance "2*1d8+2". I extract the four values OK when they are integers, but I want to be able to use floats as well for the multiplier and the addition at the end. Things get nasty when I try to parse such a string: "1.8*1d8+2.5".
I have determined that the problem is with the function strcspn. I ask it to parse the input string s (which contains the dice string) and stop at either an asterisk or an 'x':
const char * s = "1.8*1d8+2.5";
size_t l = strcspn(s,"*x");
The function should return 3, as the asterisk is at the 4th position. However, it seems to stop on the decimal separator (period) and returns 1.
It's not that I can't continue writing my function without this, as there are other ways to get things done, but still I'm curious why such a thing would happen. Has anyone ever encountered this problem before?
[EDIT]
Nevermind, I've found the answer, and it was my stupidity rather than the compiler playing tricks on me. I used this code:
if (l = strcspn(s,"*x") < strlen(s)) {
...
which returned 1 (or true) because strcspn(s,"*x") < strlen(s) evaluates to true - and was assigned to the l variable. I should have added parentheses:
if ((l = strcspn(s,"*x")) < strlen(s)) {
...
Thanks for your answers nonetheless, particularly #sleske, who made me analyse my code more deeply (which led to finding the answer).

Answer 1

There must be an error somewhere else. I wrote a test program:
#include <stdio.h>
#include <string.h>
void main(){
const char * s = "1.8*1d8+2.5";
size_t l = strcspn(s,"*x");
printf("l: %d\n", l);
}
and compiled it with gcc on Linux. On my system, it outputs "3".
Please post a complete, working example that exhibits the problem. Then we'll see...

Answer 2

Your code works just as you posted it for me1.
#include <stdio.h>
#include <string.h>
int main(void) {
const char * s = "1.8*1d8+2.5";
size_t l = strcspn(s,"*x");
printf("%zd (%.*s)\n", l, (int)l, s);
return 0;
}
so ross$ ./a.out
3 (1.8)
1. Mac OS X 10.6.4

Answer 3

I'd use sscanf instead of manually finding stop points and parsing myself. You can get your integers and floats easily out of the string with that.

Answer 4

This code:
#include <stdio.h>
#include <string.h>
int main(void)
{
const char * s = "1.8*1d8+2.5";
size_t l = strcspn(s,"*x");
printf("<<%s>> %zd <<%s>>\n", s, l, s+l);
return 0;
}
produces this answer on MacOS 10.6.4 (GCC 4.5.1):
<<1.8*1d8+2.5>> 3 <<*1d8+2.5>>
If your compiler and library does not produce the same answer, get a fixed/upgraded version of the software.
(NB: The 'z' modifier in the printf() format string is a C99 feature - it indicates that the type of the parameter is size_t.)