```{index} single: fpclassify; POSIX function ``` ```{index} single: POSIX::fpclassify; Perl function ``` # fpclassify Classify a floating-point number. ## Synopsis ```perl use POSIX qw(fpclassify FP_NAN FP_INFINITE FP_ZERO FP_SUBNORMAL FP_NORMAL); my $k = fpclassify($x); ``` ## What you get back An integer matching one of the `FP_*` constants. Compare against the symbolic names, not a hardcoded number — the values are libc implementation details. ## Differences from upstream Fully compatible with upstream POSIX. ## See also - `isnan`, `isinf`, `isfinite`, `isnormal` — narrower single-class tests.