Re: ReplacePart in an If[] construct?
- To: mathgroup at smc.vnet.net
- Subject: [mg67826] Re: ReplacePart in an If[] construct?
- From: bghiggins at ucdavis.edu
- Date: Sun, 9 Jul 2006 04:50:55 -0400 (EDT)
- References: <e8nttf$kcf$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Your code is doing exactly what you asked it to do.
The following is a compound statement
ReplacePart[#1, replaced!, 3];ReplacePart[#1, replaced!, 2]
and so the last part of it is returned in the If statement.
If you replace the above with
{ReplacePart[#1, replaced!, 3],ReplacePart[#1, replaced!, 2]}
The If statement will return both results:
(If[ (ListQ[#1] && First[#1] == 4),
{ReplacePart[#1, replaced!, 3],
ReplacePart[#1, replaced!, 2]},
#1 (*otherwise*)
] & ) /@ testList
{{3,an,example,list},{{4,another,replaced!,list},{4,replaced!,example,list}}}
Hope this helps,
Cheers
Brian
gardyloo wrote:
> Hi, all,
>
> It's probably that I'm too tired, but I have a question about using
> ReplacePart in an If[] construct. I've made up a (very) minimal example:
>
> In[1]:=
> testList = {{3, an, example, list},
> {4, another, example, list}}
>
> Out[1]=
> {{3, an, example, list}, {4, another, example, list}}
>
> In[2]:=
> (If[ (ListQ[#1] && First[#1] == 4),
> ReplacePart[#1, replaced!, 3];
> ReplacePart[#1, replaced!, 2],
> #1 (*otherwise*)
> ] & ) /@ testList
>
> Out[2]=
> {{3, an, example, list}, {4, replaced!, example, list}}
>
>
> Can someone tell me why BOTH the second and third positions in
> the second element in testList aren't turned to "replaced!" ? I have
> plenty of other ways of doing this, but this seemed the most
> straightforward, and I can't wrap my head around it, for some reason.
>
>
>
> --
> ==========================================================
> Curtis Osterhoudt
> gardyloo at mail.remove_this.wsu.and_this.edu
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