Re: ReplaceAll in If Statement
- To: mathgroup at smc.vnet.net
- Subject: [mg19489] Re: ReplaceAll in If Statement
- From: Eckhard Hennig <hennig at itwm.uni-kl.de>
- Date: Sat, 28 Aug 1999 15:53:13 -0400
- Organization: ITWM
- References: <7q20sl$q9i@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Tom Compton schrieb in Nachricht <7q20sl$q9i at smc.vnet.net>...
>In the following sequence I expected z to evaluate to 1 in the
>Module. It appears that the test in the module does not
>evaluate to either True or False. I don't understand why.
>Can anyone explain?
>
>In[1]:=
>opList={a->True};
>
>In[2]:=
>test[opts___]:=Module[{},
>If[a /. {opts}, z=1, z=2, z=3];
>{a, z} /. {opts}]
>
>In[3]:=
>test[opList]
>Out[3]=
>{{True,3}}
Tom,
note that your function call in In[3] evaluates to
test[{a->True}],
but what you wanted is
test[a->True],
i.e. the argument to test must be a Sequence of rules, not a List. With
test @@ opList
your function works correctly.
-- Eckhard
-----------------------------------------------------------
Dipl.-Ing. Eckhard Hennig mailto:hennig at itwm.uni-kl.de
Institut fuer Techno- und Wirtschaftsmathematik e.V. (ITWM)
Erwin-Schroedinger-Strasse, 67663 Kaiserslautern, Germany
Voice: +49-(0)631-205-3126 Fax: +49-(0)631-205-4139
http://www.itwm.uni-kl.de/as/employees/hennig.html
ITWM - Makers of Analog Insydes for Mathematica
http://www.itwm.uni-kl.de/as/products/ai
-----------------------------------------------------------