Re: Previous variable affects "/."
- To: mathgroup@smc.vnet.net
- Subject: [mg11261] Re: Previous variable affects "/."
- From: Allan Hayes <hay@haystack.demon.co.uk>
- Date: Wed, 4 Mar 1998 01:39:19 -0500
- References: <6dg8bd$2tr@smc.vnet.net>
Vilis Nams wrote:
>
> I am using "/." to change expressions, as follows:
>
> In[1]:= = {{1, 2}, {3, 4}, {5, 6}, {7, 8}}; In[2]:= a /. {x_,
> y_} -> {x}
> Out[2]:={1}, {3}, {5}, {7}}
> The results are expected.
>
> But, if I now define x to be something already, e.g. In[3]:= = 7;
>
> Then, when I do the Replace, Mathematica uses my previously-defined x, as follows:
>
> In[4]:= /. {x_, y_} -> {x}
> Out[4]:={7}, {7}, {7}, {7}}
Vilis
Usse :> instead of ->
In[1]:=
x = 7;
{{1, 2}, {3, 4}, {5, 6}, {7, 8}}; /. {x_, y_} :> {x}
Out[1]=
{{1},{3},{5},{7}}
--
Allan Hayes
Mathematica Training and Consulting
Leicester, UK
hay@haystack.demon.co.uk
http://www.haystack.demon.co.uk
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