WG21 N1570=04-0010
CORRECTIONS TO DOMAIN-ERROR REPORTING
FOR TR1 CHAPTER ON SPECIAL MATH FUNCTIONS
P.J. Plauger
Dinkumware, Ltd.
pjp@dinkumware.com
assoc_legendre says "a domain error occurs if m is greater than l." But
the value is well defined -- zero. Hence, a domain error should NEVER occur.
assoc_legendre says "a domain error may occur if the magnitude of x
is greater than one." But the value is always imaginary. Hence, a domain
error should ALWAYS occur.
beta says "a domain error may occur (a) if either x or y is a negative
integer, or (b) if either x or y is zero." But the beta function is
defined only for x,y > 0. Hence, a domain error should ALWAYS occur if
x <= 0 or y <= 0.
legendre says "a domain error may occur if the magnitude of x
is greater than one." But the value is always imaginary. Hence, a domain
error should ALWAYS occur.
Bessel functions all say "a domain error may occur if x is less than zero."
The various Bessels can generally be extended to negative real x, but the
functions are arguably undefined along the negative real axis. Hence, a
domain error should ALWAYS occur.