Reject NaN and infinite values.
C: isfinite detects whether a floating-point value is an ordinary finite number.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdint.h>
#include <stdbool.h>
#include <errno.h>
#include <limits.h>
#include <math.h>
#include <time.h>
int main(void) {
printf("%s\n",isfinite(1.5)?"finite":"nonfinite");
printf("%s\n",isfinite(INFINITY)?"finite":"nonfinite");
return 0;
}Expected output EXAMPLE
finite nonfinite
Details
Save as snippet.c; compile with gcc -std=c17 -Wall -Wextra snippet.c -lm -o snippet, then run ./snippet. isfinite detects whether a floating-point value is an ordinary finite number.
Tested on Ubuntu 24.04.5 LTS · · gcc (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0 · gcc 4:13.2.0-7ubuntu1
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged) / C.UTF-8
- Interpreter invocation
gcc -std=c17 -Wall -Wextra -Werror snippet.c -lm -o snippet && ./snippet- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
e706485117e0d954f0dfaee294e20a19e174f4c23859be62a635b321c9777dce- Dependencies
- gcc 4:13.2.0-7ubuntu1
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
# No input files required.
Observed standard output
finite nonfinite
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.