Re: Options for a function

• To: mathgroup at smc.vnet.net
• Subject: [mg18138] Re: Options for a function
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Fri, 18 Jun 1999 00:51:42 -0400
• Organization: Universitaet Leipzig
• References: <7ka6ub\$ins@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi Virgil,

Options[g] = {Opt1->BoxCar};
g[n_,opts___?OptionQ] :=
Module[{opt1,ans},
opt1 = Opt1 /. {opts} /. Options[g];
If[opt1 === BoxCar, ans = yes, ans = no];
{n,ans,opt1}
];

does what you want. Your function test with Equal[]
and not with Same[]. Equal[BoxCar,TEST] evaluate not to True or False
it evaluates to BoxCar==Test, this lets the local ans undefined
and you get a ans\$x.

Hope that helps
Jens

Virgil Stokes wrote:
>
> The following simple function for testing options does not work the way I expect
> (Vers. 3.0.1).
>
Options[g] = {Opt1->BoxCar};
g[n_,opts___?OptionQ] :=
Module[{opt1,ans},
opt1 = Opt1 /. {opts} /. Options[g];
If[opt1 == BoxCar, ans = yes, ans = no];
{n,ans,opt1}
];
>
> If I use
>   g[3]
> then it returns
> {3,yes,BoxCar}
> which is of course correct. However, if I use
> g[3,Opt1->TEST]
> then it returns
> {3,ans\$7,TEST}
> And, this is not what I would expect. In fact, I am
> unable to get the ans = no
>
> part of the If statement to execute. Why?
>
> -- Virgil

```

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