Re: ReplaceAll in If Statement
- To: mathgroup at smc.vnet.net
- Subject: [mg19483] Re: [mg19448] ReplaceAll in If Statement
- From: "Tomas Garza" <tgarza at mail.internet.com.mx>
- Date: Sat, 28 Aug 1999 15:53:09 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Tom Compton [comptont at concentric.net] wrote:
> 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}}
Leave the braces out in {opts}:
In[1]:=
test2[opts___] := Module[{},
If[a /. opts, z = 1, z = 2, z = 3];
{a, z} /. opts]
In[2]:=
test2[opList]
Out[2]=
{True, 1}
Since a/.{opList} gives {True}, this is neither True or False.
Tomas Garza
Mexico City