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Postings from May 2005
From: Edward Cherlin
May 19, 2005 02:06
Message ID: email@example.com
There was a discussion of the principal value of square root on
this list some time back, making the point that for positive
real numbers the positive square root is the value of the
standard function. In the complex plane it is desirable to
define the principal value at every point so as to produce a
minimum of surprises, such as sudden jumps at discontinuities.
However, there must necessarily be a line of discontinuity.
Similarly for other complex-valued functions, particularly the
trig and inverse trig functions, some of which are
It turns out that the domain and range and the location of the
cut lines have to be worked out separately for different
functions. Mathematical practice is not entirely consistent in
making these decisions, but in programming, there seems to be
widespread agreement that the shared definitions used in the
APL, Common LISP, and Ada standards are the best available.
Do we want to get into all of this in Perl6?
Generalist & activist--Linux, languages, literacy and more
"A knot! Oh, do let me help to undo it!"
--Alice in Wonderland
by Edward Cherlin