#9710: Assumptions not passed to differential equation solver
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Reporter: kedlaya | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone:
Component: calculus | Keywords: differential equations, assumptions
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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The assume function doesn't seem to work with the differential equation
solver, despite what the documentation for desolve suggests. This returns
an error:
{{{
sage: x = var('x')
sage: k = var('k')
sage: y = function('y',x)
sage: assume(k>0)
sage: print desolve(diff(y,x,x)+k*y-exp(-k*x),[y,x])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "_sage_input_25.py", line 10, in <module>
exec compile(u'open("___code___.py","w").write("# -*- coding: utf-8
-*-\\n" +
_support_.preparse_worksheet_cell(base64.b64decode("eCA9IHZhcigneCcpCmsgPSB2YXIoJ2snKQp5ID0gZnVuY3Rpb24oJ3knLHgpCmFzc3VtZShrPjApCnByaW50IGRlc29sdmUoZGlmZih5LHgseCkrayp5LWV4cCgtayp4KSxbeSx4XSk="),globals())+"\\n");
execfile(os.path.abspath("___code___.py"))
File "", line 1, in <module>
File "/tmp/tmpyNFGr0/___code___.py", line 7, in <module>
exec compile(u'print desolve(diff(y,x,x)+k*y-exp(-k*x),[y,x])
File "", line 1, in <module>
File "/home/kedlaya/sage-complete/local/lib/python2.6/site-
packages/sage/calculus/desolvers.py", line 340, in desolve
soln = maxima(cmd)
File "/home/kedlaya/sage-complete/local/lib/python2.6/site-
packages/sage/interfaces/expect.py", line 1032, in __call__
return cls(self, x, name=name)
File "/home/kedlaya/sage-complete/local/lib/python2.6/site-
packages/sage/interfaces/expect.py", line 1451, in __init__
raise TypeError, x
TypeError: Computation failed since Maxima requested additional
constraints (try the command 'assume(k>0)' before integral or limit
evaluation, for example):
Is k positive, negative, or zero?
}}}
Found by Praveen N. and Aashita during Sage Days 25 coding sprint.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9710>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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