       Re: Tips for writing correct, non trivial Mathematica Libraries

• To: mathgroup at smc.vnet.net
• Subject: [mg124452] Re: Tips for writing correct, non trivial Mathematica Libraries
• From: Nehal Patel <nehal.alum at gmail.com>
• Date: Fri, 20 Jan 2012 01:50:20 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201201191012.FAA03722@smc.vnet.net> <3609A129-8BFE-453D-B414-9C1D4366BA43@mimuw.edu.pl> <A0087CCC-AB33-4507-A793-9806842F1832@gmail.com> <02BFEBF3-35C4-4C4E-83B7-E0A4EDBF6512@mimuw.edu.pl>

```>> of x + y to be  Sqrt[x y], it should be (x + y)^1 = x+ y
>
> No, it shouldn't be. There is no such thing as a mean of a number or
an algebraic expression. What you would expect is

But something like Times should be ok?  It think it's a reasonable
matter of convention whether someone feels like a definition for
geometric mean should expect a single vector argument, or as multiple
arguments e.g. geom[x,y,z,=85]  but I'll admit we're quibbling at this
point and move on.

>
> Clear[geom]
>
> geom::nonlist =
>  "The argument `1` is neither a non-empty vector nor a non-empty matrix";
>
> geom[ls_] /;If[Head[ls] === List, True, Message[geom::nonlist, x]; False] :=
> Apply[Times, ls]^(1/Length[ls])

Awesome -- this is what I was curious about!  Thanks for taking the time.

```

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