[Maxima-bugs] [ maxima-Bugs-1860250 ] erf(-inf)

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Bugs item #1860250, was opened at 2007-12-28 18:58
Message generated for change (Comment added) made by willisbl
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Category: Lisp Core - Simplification
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Barton Willis (willisbl)
Assigned to: Barton Willis (willisbl)
Summary: erf(-inf)

Initial Comment:
OK

(%i3) erf(inf);
(%o3) 1

Not OK

(%i4) erf(-inf);
(%o4) -erf(inf)

(%i5) ev(%);
(%o5) -1

Also

(%i1) tellsimpafter(erf(z), 42/100);
(%o1) [erfrule1,simperf]

Not OK

(%i2) erf(-z);
(%o2) -erf(z)

(%i3) ev(%);
(%o3) -21/50



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>Comment By: Barton Willis (willisbl)
Date: 2008-01-10 13:23

Message:
Logged In: YES 
user_id=895922
Originator: YES

Fixed by csimp2 CVS version 1.19. Appended regression tests to rtest16.

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Comment By: Barton Willis (willisbl)
Date: 2007-12-29 06:34

Message:
Logged In: YES 
user_id=895922
Originator: YES

Proposed fix (untested):

(defmfun simperf (x vestigial z &aux y)
  (declare (ignore vestigial))
  (oneargcheck x)
  (setq y (simpcheck (cadr x) z))
  (cond ((zerop1 y) y)
	((or (floatp y) (and $numer (integerp y))) (erf (float y)))
	((eq y '$inf) 1)
	((eq y '$minf) -1)
	;;((and $trigsign (mminusp* y)) (neg (list '(%erf simp) (neg y))))
	((and $trigsign (great (neg y) y)) (neg (take '(%erf) (neg y))))
	(t (eqtest (list '(%erf) y) x))))

The user documentation doesn't say that trigsign == false prevents erf
from doing a reflection simplification. 



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