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MathGroup Archive 2005

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A few usage based questions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61153] A few usage based questions
  • From: "Matt" <anonmous69 at netscape.net>
  • Date: Tue, 11 Oct 2005 03:22:27 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello,
  any light shed on the following would be appreciated:

Question 1:  If I wanted to experiment with ReplaceAll and
ReplaceRepeated, how would I use a variable to achieve this?

e.g.  I tried this:
replaceType = /.; (* replaceType would also be //. for subsequent
runs*)
(* initialize counter *)
counter = 0;
resultOne = (2 a M[1] M[
  2] M[] + 3 b M[1, 3] M[2] M["s"] + Log[f[
        M[1] M[1.2] M[3.4] M[M]]]) replaceType {m1_M
        m2_M :> (++counter; MContainer[m1, m2])}


but got the following error:
Syntax::sntxb : Expression cannot begin with "replaceType = /.;".
More...

What I was trying to achieve (for an obviously longer example) was to
be able to set the type of replace I wanted to do at the beginning of
the cell, then use that symbolic name inside of the actual 'code'.
BTW, the sample I am attempting to modify is from page 615 of Michael
Trott's "The Mathematica Guidebook for Programming".


Question 2:  What is the correct method to limit the types of values a
function will accept?
If I wanted to constrain the argument type of a function to be all
reals, is this the right way?
f[x_Real|x_Integer] := something
The above works, but I haven't seen my attempt confirmed in any
documentation.


Question 3:  How do I know what a function returns?  (e.g. a boolean or
Null or an integer, a string, etc.)


Thanks much,

Matt


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