Re: What does & mean?

• To: mathgroup at smc.vnet.net
• Subject: [mg107069] Re: [mg107050] What does & mean?
• From: Tomas Garza <tgarza10 at msn.com>
• Date: Tue, 2 Feb 2010 03:26:25 -0500 (EST)
• References: <201002011114.GAA22737@smc.vnet.net>

```I understand your plight. What you are wondering about (&) is right at the heart of Mathematica, in the topic of Functional Programming. Look in the Help|Documentation Center for Function (or &). This will take you to the concept of "pure functions" and related stuff. It will look rather obscure at first, but if you have patience and work through the tutorials, you'll find that it is extremely useful. Also, you may go to the bottom of the Help|Documentation Center, select the  'How to' Topics and then "How to work with variables and functions - Work with Pure Functions". There you'll find a lot of information and you'll be introduced to functional programming. It works wonders!

Tomas

> Date: Mon, 1 Feb 2010 06:14:23 -0500
> From: micknudsen at gmail.com
> Subject: [mg107050] What does & mean?
> To: mathgroup at smc.vnet.net
>
> Hi,
>
> I have recently bought Mathematica, and I have a really tough time
> getting started. I'm reading the various documents found under
> "Complete Documentation" at the Mathematica homepage, but it doesn't
> feel like the right place to start.
>
> For example, I'm now trying to solve some simple differential
> equations, and the documentation provides the following example:
>
> A = {{4, -6}, {1,-1}};
>
> X[t_] = {x[t], y[t]};
> system = MapThread[#1 == #2 &, {X'[t], A.X[t]}];
>
> sol = DSolve[system, {x,y}, t]
>
> However, there is no explanation of how & works here (and it isn't in
> the MapThread documentation either). Where should one start reading in
> order to understand basic constructs like this? This particular
> example is really nasty, since & is generally ignored by search
> engines.
>
> Thanks,
> Michael Knudsen
>

```

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