Re: ReplacePart in an If[] construct?
- To: mathgroup at smc.vnet.net
- Subject: [mg67819] Re: [mg67816] ReplacePart in an If[] construct?
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Sun, 9 Jul 2006 04:50:37 -0400 (EDT)
- References: <200607080857.EAA20495@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
On 8 Jul 2006, at 09:57, 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. They are indeed both "replaced", but only the second one is RETURNED. Note that ReplacePart does not change its first argument: a= {4, another, example, list}; ReplacePart[a,replaced!,3] {4,another,replaced!,list} a {4,another,example,list} Andrzej Kozlowski Oxford, UK
- References:
- ReplacePart in an If[] construct?
- From: gardyloo <gardyloo@mail.wsu.edu>
- ReplacePart in an If[] construct?