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Re: slot argument weirdness

  • To: mathgroup at smc.vnet.net
  • Subject: [mg83929] Re: slot argument weirdness
  • From: Tom Burton <news at brahea.com>
  • Date: Wed, 5 Dec 2007 07:02:13 -0500 (EST)

Considering that all the examples of slots in online help (Slot) show  
slots inside of pure functions, where is the weirdness: in the slots,  
or in your attempt to use them outside their native habitat?

You're so close :-)  How about?

m={{#1,#2},{#2,#1}}&;
Apply[m, v]

Simple pure functions are fine, but complex ones can be hard to read.  
How about instead a regular function,

m=Function[{u,v},{{u,v},{v,u}}]

or a rule?

r={u_,v_}:>{{u,v},{v,u}};
v/.r

Tom

When responding, please replace news with my first initial and full  
last name, as one word.

Tom Burton

> I have to produce some bulky matrices which are described by two  
> parameters and it seems the easiest way to produce them is as  
> follows (I took out all the complexity and just left in the slots  
> to illustrate my problem). v is the parameter array.
>
> v = {2, 5};
>
> ... but since the actual form in the first argument in Apply is  
> really a large messy thing, I thought I'd produce it just once in  
> the notebook and represent it with:
>
> m = {{#1, #2}, {#2, #1}};
>
> But geez, this doesn't work at all ...



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