Limits & predicates with options.
- To: mathgroup at smc.vnet.net
- Subject: [mg6999] Limits & predicates with options.
- From: Jack Goldberg <jackgold at math.lsa.umich.edu>
- Date: Thu, 1 May 1997 14:48:45 -0400 (EDT)
- Organization: Mathematics Department, University of Michigan
- Sender: owner-wri-mathgroup at wolfram.com
I need some guidance in handling this call:
because the function f[x,a] is constructed deep inside other code.
I want to take different actions depending on whether this limit exists.
However, I don't know how to distinguish these alternatives without
staring at the result. The problem seems to be that Limit can return a
far larger set of outputs than I initially (and somewhat naively)
thought. Besides the obvious, Limit can return this
whose Head is Times. So "head" testing doesn't seem like a good idea. I
am stuck here.
What I would like ideally is a Predicate, say, LimitQ[...] which
returns True if the limit exists and False otherwise. Of course, at
this level of generality, one might have to wait forever for an answer!
Which leads me to a second question.
Can Predicates have options? In this case and obvious option would be a
time constraint: The output is False, if CPU time exceeds a preset
University of Michigan
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