Re: Evaluation question
- To: mathgroup at smc.vnet.net
- Subject: [mg82175] Re: Evaluation question
- From: Szabolcs Horvát <szhorvat at gmail.com>
- Date: Sun, 14 Oct 2007 06:06:16 -0400 (EDT)
- References: <200710120656.CAA04613@smc.vnet.net> <fepuqv$hvl$1@smc.vnet.net> <47109042.2000302@gmail.com>
Szabolcs Horvát wrote:
> It seems that Rule and RuleDelayed are "evaluated to themselves":
>
> In[1]:= Trace[1->2+3]
> Out[1]= {{2+3,5},1->5,1->5}
>
> In[2]:= Attributes[f]=Attributes[Rule]
> Out[2]= {Protected,SequenceHold}
>
> In[3]:= Trace[f[1,2+3]]
> Out[3]= {{2+3,5},f[1,5]}
>
Block[] can free Rule from this special behaviour:
In[1]:= Block[{Rule},1->Unevaluated[2+3]]//Trace
Out[1]=
{Block[{Rule},1->Unevaluated[2+3]],{1->2+3,1->Unevaluated[2+3]},1->Unevaluated[2+3],1->2+3,1->2+3,{2+3,5},1->5,1->5}
--
Szabolcs
- References:
- Evaluation question
- From: Yaroslav Bulatov <yaroslavvb@gmail.com>
- Evaluation question