#11776: Holding an expression unevaluated: Something like hold_all() would be
nice.
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Reporter: Pap | Owner: jason
Type: enhancement | Status: new
Priority: minor | Milestone: sage-4.7.2
Component: misc | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by nbruin):
Given that {{{expression}}} is already evaluated (leading to a simplified
expression) before {{{hold_all}}} even gets a hold of it, this approach is
a little problematic. The basic feature is already available, but perhaps
not very convenient for your taste. See {{{sin(pi,hold=True)}}}. Currently
this isn't available for integrals etc., but there is
{{{sage.calculus.calculus.dummy_integrate(x^2+1,x)}}}
It is very reasonable to ask for {{{integrate(x^2+1,x,hold=True)}}} to be
synonymous with that.
You can already do
{{{
def held(f):
return lambda *args: f(*args,hold=True)
sin=held(sin)
cos=held(cos)
sin(pi)^2+cos(pi)^2
}}}
one could have a package inert_symbolic_functions that has (essentially)
those declarations, so that a
{{{
from held_symbolic_functions import *
}}}
would give you a "held" environment. With a little namespace injection
magic one could probably also use that to implement
{{{
with held_function_context:
expr=sin(pi)^2+cos(pi)^2
}}}
which is probably the closest to what you request, subject to being doable
in python.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11776#comment:1>
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