#7742: add a compose function to sage
------------------------------------------------+---------------------------
Reporter: was | Owner: AlexGhitza
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.6.1
Component: basic arithmetic | Keywords:
Author: Christopher Olah, Felix Lawrence | Upstream: N/A
Reviewer: Paul Zimmermann | Merged:
Work_issues: |
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Comment(by zimmerma):
Replying to [comment:12 flawrence]:
> * compose(f,g)(x) = f(g(x)) - is this the most common convention among
mathematicians? or should the RHS be g(f(x))?
compose(f,g) seems good to me.
> * Is (f, n, a) or (f, a, n) the best order of parameters for nest?
I prefer (f,n,a) since this is coherent with {{{self_compose(f,n)}}}.
> * Is there somewhere more suitable than misc/misc.py for these
functions?
I don't know.
Also if a symbolic n is not allowed (yet) in {{{self_compose}}}, some
type-checking
should be done:
{{{
sage: function('f')
sage: var('m')
sage: self_compose(f,m)(x)
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/localdisk/tmp/sage-4.6/<ipython console> in <module>()
/localdisk/tmp/sage-4.6/local/lib/python2.6/site-
packages/sage/misc/misc.pyc in self_compose(f, n)
890 # all necessary powers of two (f, f^2, f^4), storing them in a
list
891 fs = [f]
--> 892 for i in xrange(int(floor(log(n, 2)))):
893 fs.append(compose(fs[i], fs[i]))
894
/localdisk/tmp/sage-4.6/local/lib/python2.6/site-
packages/sage/symbolic/expression.so in
sage.symbolic.expression.Expression.__float__
(sage/symbolic/expression.cpp:5398)()
TypeError: unable to simplify to float approximation
}}}
Paul
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7742#comment:16>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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