HYPOT(3) NetBSD Library Functions Manual HYPOT(3)NAME

hypot,hypotf,cabs,cabsf-- Euclidean distance and complex absolute value functionsLIBRARY

Math Library (libm, -lm)SYNOPSIS

#include <math.h>doublehypot(double x,double y);floathypotf(float x,float y);doublecabs(struct complex { double x; double y; } z);floatcabsf(struct complex { float x; float y; } z);DESCRIPTION

Thehypot() andcabs() functions compute the sqrt(x*x+y*y) in such a way that underflow will not happen, and overflow occurs only if the final result deserves it.hypot(infinity,v) =hypot(v,infinity) = +infinity for allv, includingNaN.ERRORS

Below 0.97ulps. Consequentlyhypot(5.0,12.0) = 13.0 exactly; in gen- eral, hypot and cabs return an integer whenever an integer might be expected. The same cannot be said for the shorter and faster version of hypot and cabs that is provided in the comments in cabs.c; its error can exceed 1.2ulps.NOTES

As might be expected,hypot(v,NaN) andhypot(NaN,v) areNaNfor allfinite v; with "reserved operand" in place of "NaN", the same is true on a VAX. But programmers on machines other than a VAX (it has no infinity) might be surprised at first to discover thathypot(±infinity,NaN) = +infinity. This is intentional; it happens becausehypot(infinity,v) = +infinity forall v, finite or infinite. Hencehypot(infinity,v) is independent ofv. Unlike the reserved operand fault on a VAX, the IEEENaNis designed to disappear when it turns out to be irrelevant, as it does inhypot(infinity,NaN).SEE ALSO

math(3), sqrt(3)HISTORY

Both ahypot() function and acabs() function appeared in Version 7 AT&T UNIX.BUGS

Thecabs() andcabsf() functions use structures that are not defined in any header and need to be defined by the user. As such they cannot be prototyped properly. NetBSD 4.0 May 6, 1991 NetBSD 4.0

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