#8237: Sage does not recognize Maxima's complex infinity
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Reporter: robert.marik | Owner: burcin
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.3.4
Component: symbolics | Keywords:
Author: Burcin Erocal | Upstream: N/A
Reviewer: Karl-Dieter Crisman, Ross Kyprianou | Merged:
Work_issues: |
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Changes (by rossk):
* reviewer: Karl-Dieter Crisman => Karl-Dieter Crisman, Ross Kyprianou
Comment:
By exercising a number of arithmetic use cases, viz.
{{{
for k in (1, 1.0, 1/2, x, 1+I, -1, -1.0, -1/2, -x, -1-I):
print k, k + Infinity , k + +Infinity, k + -Infinity
for k in (1, 1.0, 1/2, x, 1+I, -1, -1.0, -1/2, -x, -1-I):
print k, Infinity -k , +Infinity -k, -Infinity -k
for k in (1, 1.0, 1/2, x, 1+I, -1, -1.0, -1/2, -x, -1-I):
print k, k / Infinity , k / +Infinity, k / -Infinity
for k in (1, 1.0, 1/2, x, -1, -1.0, -1/2, -x):
print k, k * Infinity , k * +Infinity, k * -Infinity
}}}
there were a small number of things to note[[BR]]
(a) the same answer resulted, regardless of whether (unsigned) Infinity or
+Infinity was used. Query: Just to make sure we are getting the results we
designed for... Currently +Infinity (or -Infinity) is being returned
regardless of whether a signed or unsigned infinity is used. Should
(unsigned) Infinity be returned when (unsigned) Infinity is used?[[BR]]
(b) what seems to be an inconsistency occurs when mixing Infinity with
complex numbers (same thing holds when we replace Infinity with +Infinity
or with -Infinity)
{{{
# the following combinations of complex and infinity are ok
I + Infinity # +Infinity
I - Infinity # -Infinity
I / Infinity # 0
# the following crash with Arithmetic Error
Infinity / I
Infinity * I
I * Infinity
# isnt I+Infinity (for example) just as meaningful/less as I*Infinity ?
}}}
(c) Im curious about the following expressions
{{{
x * Infinity
-x * Infinity
}}}
These return {{{+Infinity}}} and {{{-Infinity}}} respectively. But what if
x is negative real? (should be opposite answers). The following tries to
demonstrate this for two vars (z and x), both declared real in two
different ways
{{{
sage: var('z',domain='real')
z
sage: assume(x,'real',x<0,z<0)
sage: assumptions()
[x is real, x < 0, z < 0]
sage: x*+Infinity
+Infinity
sage: z*+Infinity
+Infinity
}}}
(is this another ticket "make Infinity work with
assumptions/declarations"?)
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8237#comment:9>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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