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The documentation on OptionsPattern leaves me with some unanswered questions. From the example section:

Options[f] = {a -> a0, b -> b0}; 

f[x_, OptionsPattern[]] := {x, OptionValue[a]}

f[7, a -> uuu]
(* {7, uuu} *)

I don't think using global symbols for the named Options is a great idea so I wonder how to localise them / make sure there isn't going to be any conflict with other definitions in the same document?

a=1;
f[7, a -> uuu]
(* {f[7, 1 -> uuu], a0} *)
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    $\begingroup$ A somehwat relevant discussion. Since that post, I have changed my views a little, now I use strings as option names somewhat more often than before. $\endgroup$ Jan 27, 2015 at 17:21

3 Answers 3

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Some built-in functions use strings as option names:

Options[f] = {"AnObscureOption" -> 1};
f[x_, OptionsPattern[]] := {x, OptionValue["AnObscureOption"]}

Advantages of this are that the global namespace is not cluttered with extra symbols and they do not have to be write protected but there is a disadvantage in that they are not amenable to usage type documentation:

"AnObscureOption"::usage = "\"AnObscureOption\" is an obscure option for function f.";

Message::name: Message name "AnObscureOption"::usage is not of the form symbol::name or symbol::name::language.

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    $\begingroup$ Just seen @tchronis's answer -- must type faster! Guess I'll leave mine for now as I mention a disadvantage of string option names. $\endgroup$ Jan 27, 2015 at 14:52
  • $\begingroup$ You are very welcome @MikeLimaOscar. Indeed strings cannot have a usage. $\endgroup$
    – tchronis
    Jan 27, 2015 at 14:56
  • $\begingroup$ Bigger disadvantage for me is that I can't use auto-completion with them. (But yes, I also use strings.) $\endgroup$
    – Szabolcs
    Jan 27, 2015 at 15:47
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It is normal for option variables to be global and to be given the property Protected, which will prevent assigning to them. In your example, you would write

Protect[a, b]; Options[f] = {a -> a0, b -> b0};

then

a = 1;
Set::wrsym: Symbol a is Protected. >>
a
a
Attributes[a]
 {Protected}

and similarly for b.

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Instead of protecting option variables that is sacrifice useful names,

I generally use meaningful strings:

Options[f] = {"a" -> a0, "b" -> b0};

f[x_, OptionsPattern[]] := {x, OptionValue["a"]}

Any objections are very welcomed but this worked for me so far.

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