HYPOT(3) BSD Programmer's Manual HYPOT(3)
h
\bhy
\byp
\bpo
\bot
\bt, c
\bca
\bab
\bbs
\bs - euclidean distance and complex absolute value functions
S
\bSY
\bYN
\bNO
\bOP
\bPS
\bSI
\bIS
\bS
#
\b#i
\bin
\bnc
\bcl
\blu
\bud
\bde
\be <
\b<m
\bma
\bat
\bth
\bh.
\b.h
\bh>
\b>
h
\bhy
\byp
\bpo
\bot
\bt(_
\bd_
\bo_
\bu_
\bb_
\bl_
\be _
\bx, _
\bd_
\bo_
\bu_
\bb_
\bl_
\be _
\by);
s
\bst
\btr
\bru
\buc
\bct
\bt {
\b{d
\bdo
\bou
\bub
\bbl
\ble
\be x
\bx,
\b, y
\by;
\b;}
\b} z
\bz;
\b;
D
\bDE
\bES
\bSC
\bCR
\bRI
\bIP
\bPT
\bTI
\bIO
\bON
\bN
The h
\bhy
\byp
\bpo
\bot
\bt() and c
\bca
\bab
\bbs
\bs() functions computes the sqrt(x*x+y*y) in such a way
that underflow will not happen, and overflow occurs only if the final re-
h
\bhy
\byp
\bpo
\bot
\bt(_
\bi_
\bn_
\bf_
\bi_
\bn_
\bi_
\bt_
\by, _
\bv) = h
\bhy
\byp
\bpo
\bot
\bt(_
\bv, _
\bi_
\bn_
\bf_
\bi_
\bn_
\bi_
\bt_
\by) = +infinity for all _
\bv, including
E
\bER
\bRR
\bRO
\bOR
\bR (
\b(d
\bdu
\bue
\be t
\bto
\bo R
\bRo
\bou
\bun
\bnd
\bdo
\bof
\bff
\bf,
\b, e
\bet
\btc
\bc.
\b.)
\b)
Below 0.97 _
\bu_
\bl_
\bp_
\bs. Consequently h
\bhy
\byp
\bpo
\bot
\bt(_
\b5_
\b._
\b0, _
\b1_
\b2_
\b._
\b0) = 13.0 exactly; in gener-
al, hypot and cabs return an integer whenever an integer might be expect-
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 1.2
As might be expected, h
\bhy
\byp
\bpo
\bot
\bt(_
\bv, _
\bN_
\ba_
\bN) and h
\bhy
\byp
\bpo
\bot
\bt(_
\bN_
\ba_
\bN, _
\bv) are _
\bN_
\ba_
\bN for all
_
\bf_
\bi_
\bn_
\bi_
\bt_
\be _
\bv; with "reserved operand" in place of "_
\bN_
\ba_
\bN", the same is true on
a VAX. But programmers on machines other than a VAX (if has no infinity)
might be surprised at first to discover that h
\bhy
\byp
\bpo
\bot
\bt(_
\b+_
\b-_
\bi_
\bn_
\bf_
\bi_
\bn_
\bi_
\bt_
\by, _
\bN_
\ba_
\bN) =
+infinity. This is intentional; it happens because h
\bhy
\byp
\bpo
\bot
\bt(_
\bi_
\bn_
\bf_
\bi_
\bn_
\bi_
\bt_
\by, _
\bv) =
+infinity for _
\ba_
\bl_
\bl _
\bv, finite or infinite. Hence h
\bhy
\byp
\bpo
\bot
\bt(_
\bi_
\bn_
\bf_
\bi_
\bn_
\bi_
\bt_
\by, _
\bv) is in-
dependent of _
\bv. Unlike the reserved operand fault on a VAX, the IEEE _
\bN_
\ba_
\bN
is designed to disappear when it turns out to be irrelevant, as it does
in h
\bhy
\byp
\bpo
\bot
\bt(_
\bi_
\bn_
\bf_
\bi_
\bn_
\bi_
\bt_
\by, _
\bN_
\ba_
\bN).
S
\bSE
\bEE
\bE A
\bAL
\bLS
\bSO
\bO
H
\bHI
\bIS
\bST
\bTO
\bOR
\bRY
\bY
Both a h
\bhy
\byp
\bpo
\bot
\bt() function and a c
\bca
\bab
\bbs
\bs() function appeared in Version 7 AT&T
4th Berkeley Distribution June 4, 1993 1
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