[Proj] A tangential aside
Gerald I. Evenden
geraldi.evenden at gmail.com
Fri Aug 29 14:34:39 EDT 2008
I knew that using tan(x) as a function example would likely agitate the ivory
tower math types but I suspect most of us down and dirty applied programmers
treat it as a simple function and avoid tan's nasty behavior near |pi/2| by
having tolerance tests of the argument and thus seek an alternate program
route if there is going to be a problem. You will find many of these tests
within the libproj4 library code and a whole section of added functions that
provide argument range testing before calling transcendental functions
entries with the sole purpose of providing a known course of action before a
funky operation occurs.
Some of these test date back to the GCTP days in the '60s.
As pointed out, some cpu's provide enhanced status indicators as to what
happened during a function evaluation; but relying upon this feature
compromises machine independent code.
The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist
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