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Re: Function parameters, using : and ?

• To: mathgroup at smc.vnet.net
• Subject: [mg2831] Re: [mg2813] Function parameters, using : and ?
• From: Allan Hayes <hay at haystack.demon.co.uk>
• Date: Sat, 23 Dec 1995 03:18:24 -0500

rmarimon at leland.stanford.edu (Ricardo Marimon)
>Subject: [mg2813] Function parameters, using : and ?
Finds that the following does not work

   Func[x_List, y_List, epsilon_(?NumberQ):10^-6] := Module[{},...]

Ricardo:
The following variants work

   Func[x_List, y_List, epsilon:_?(NumberQ):10^-6] := Module[{},...]
   Func[x_List, y_List, epsilon:(_?NumberQ):10^-6] := Module[{},...]


Using HoldForm[FullForm[....]] each of the third entries gives the form

   Optional[
   	Pattern[epsilon, PatternTest[Blank[], NumberQ]],
   	Power[10, -6]
   ]

The abbreviation x_ for x:_ does not parse properly.

Allan Hayes
hay at haystack.demon.co.uk