Re: With[{software=Mathematica}, Frustration]
- To: mathgroup at smc.vnet.net
- Subject: [mg24335] Re: [mg24308] With[{software=Mathematica}, Frustration]
- From: BobHanlon at aol.com
- Date: Sun, 9 Jul 2000 04:52:43 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
In a message dated 7/7/2000 12:44:38 AM, siegman at stanford.edu writes:
>Pages 359-360 of The Mathematica Book says (admittedly, taken a little
>
>out of context),
>
> "You can think of With as a generalization of the /. operator. . ."
>
>and
>
> " With[{x=x0}, body] works essentially like body /. x->x0 . . . "
>
>Great, looks neat, let's try it for evaluating expressions without
>permanently setting the variables in them:
>
> In[1]:= c = a b
>
> Out[1]= a b
>
> In[2]:= c
>
> Out[2]= a b
>
> In[10]:= c /. {a -> 2, b -> 3}
>
> Out[10]= 6
>
> In[3]:= With[{a = 2, b = 3}, c]
>
> Out[3]= a b
>
>*Not* what I was hoping for . . .
>
Attributes[With]
{HoldAll, Protected}
c = a*b;
With[{a = 2, b = 3}, Evaluate[c]]
6
Bob Hanlon