#15025: automatically injected function does not work with desolve
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Reporter: dkrenn | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-5.12
Component: symbolics | Keywords: desolve function
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Dependencies: | Stopgaps:
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The following does not work:
{{{
sage: x = var('x')
sage: f = function('y', x)
sage: desolve(diff(y,x)-y == 0,y)
Traceback (click to the left of this block for traceback)
...
TypeError
}}}
altough {{{y}}} is automatically injected to the gobal namespace.
This is because {{{y}}} is of the wrong type:
{{{
sage: f, type(f)
(y(x), sage.symbolic.expression.Expression)
sage: y, type(y)
(y, sage.symbolic.function_factory.NewSymbolicFunction)
}}}
It works with {{{f}}}:
{{{
sage: desolve(diff(f,x)-f == 0,f)
c*e^x
}}}
This is confusing, especially, since in the docstring of {{{function}}}
under "Note" you can find
> The new function is both returned and automatically injected into the
global namespace.
Therefore, it is not absurd to assume that this automatically injected
variable is the one I want to use, i.e. the one you would get by {{{y =
function('y', x)}}} (similar to the {{{var}}}-command).
(If this is behavior of {{{function}}} is (really) on purpose, then at
least the error message of {{{desolve}}} should be more clearifying and
give a hint.)
--
Ticket URL: <http://trac.sagemath.org/ticket/15025>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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