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MathGroup Archive 2007

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Re: Defining a Function with an Indeterminate Number of Arguments

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81279] Re: [mg81244] Defining a Function with an Indeterminate Number of Arguments
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Tue, 18 Sep 2007 00:43:30 -0400 (EDT)
  • References: <21953058.1190070499180.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

fnc1[args___] := Module[{}, values = {args};
   Print["Argument Values: "];
   Table[Print[i, "   ", values[[i]], " Head ", Head[values[[i]]]], {i,
      Length[values]}];];(*End Module*)fnc1[b, 3, "strg1"]

Argument Values:

1   b Head Symbol

2   3 Head Integer

3   strg1 Head String

Bobby

On Mon, 17 Sep 2007 02:37:09 -0500, Donald DuBois <donabc at comcast.net>  
wrote:

> Hello -
>
> I am trying to define a function with the following two properties :
>  (A) The function should be able to take an indeterminate number of
> arguments without using the List structure (like the Which or StringJoin  
> functions in Mathematica).
>  (B) The function should have the capability of defining and using  
> options in the usual way  (i.e. using the Options function outside the 
> package definition
> to define the option default values and using OptionValue within the  
> function definition to retrieve the options with locally defined option  
> values overriding the default values).
>
> As a first attempt, fnc1 below is able to have as
> input an indeterminate number of arguments.
>
> fnc1[args : _ ..] := Module[{},
>    values = args;
>   Print["Argument Values: "];
>    Table[Print[i, "   ", {values}[[i]], " Head ",
>      Head[{values}[[i]]]], {i, Length[{values}]}];
>    ]; (* End Module *)
>
> fnc1[b, 3, "strg1"]
>
> Argument Values:
>
> 1   b Head Symbol
>
> 2   3 Head Integer
>
> 3   strg1 Head String
>
>
> However, when I try (in fnc2 below) to define default option values in
> the usual way for this function, I am unable to retrieve them - only the  
> locally defined option values (opt1 in the e.g. below) become known to 
> the function.
>
>
> (* Define Default Options *)
> Options[fnc2] =
>     {
>       opt1 -> 10,
>       opt2 -> 20
>       };
>
> fnc2[args : _ ..] := Module[{},
>      (* Extract the non-rule arguments from args *)
>      values = Cases[{args}, Except[_Rule]];
>      Print["Argument Values: "];
>       Table[
>     Print[i, "   ", values[[i]], " Head ", Head[values[[i]]]], {i,
>      Length[values]}];
>      (* Extract the options from args *)
>       localOpts = Cases[{args}, _Rule];
>      Print["local options list = ", localOpts];
>   Print["Final Option Values: "];
>       Print["opt1 = ",
>         localOpts /. OptionsPattern[] :> OptionValue[opt1]];
>       Print["opt2 = ",
>         localOpts /. OptionsPattern[] :> OptionValue[opt2]];
>      ] (* End Module *);
>
> fnc2[b, 3, "strg1", opt1 -> 15]
>
> Argument Values:
>
> 1   b Head Symbol
>
> 2   3 Head Integer
>
> 3   strg1 Head String
>
> local options list = {opt1->15}
>
> Final Option Values:
>
> opt1 = 15
>
> opt2 = opt2
>
>
> There is a messy workaround  (fnc3 below) but the default option values  
> are redefined every time it is used.
>
> fnc3[args : _ ..] := Module[{},
>         defaultOpts = {opt1 -> 10, opt2 -> 20};
>      (* Extract the non-rule arguments from args *)
>       values = Cases[{args}, Except[_Rule]];
>      Print["Argument Values: "];
>       Table[
>     Print[i, "   ", values[[i]], " Head ", Head[values[[i]]]], {i,
>           Length[values]}];
>      (* Extract the local options from args *)
>       localOpts = Cases[{args}, _Rule];
>       Print["local options list = ", localOpts];
>    Print["default options list = ", defaultOpts];
>   (* Combine localOpts with defaultOpts where localOpts take
>    precedence *)
>   combinedOpts =
>     Flatten[Split[Sort[Join[defaultOpts, localOpts]],
>        First[#1] === First[#2] &] /. {dd_Rule, ddd_Rule} -> ddd];
>   Print["Final Combined Option Values: "];
>       Print["opt1 = ",
>         combinedOpts /. OptionsPattern[] :> OptionValue[opt1]];
>       Print["opt2 = ",
>         combinedOpts /. OptionsPattern[] :> OptionValue[opt2]];
>      ]; (* End Module *)
>
> fnc3[b, 3, "strg1", opt1 -> 15]
>
> Argument Values:
>
> 1   b Head Symbol
>
> 2   3 Head Integer
>
> 3   strg1 Head String
>
> local options list = {opt1->15}
>
> default options list = {opt1->10,opt2->20}
>
> Final Combined Option Values:
>
> opt1 = 15
>
> opt2 = 20
>
> Is there a way to define a function that has the two properties, (A and  
> B above) so that it takes an indefinite number of arguments (without the  
> List curly brackets or List function) and where options can be defined 
> using the Options and OptionValue functions in the usual way?
>
> Thank you in advance,
>
> Don
>
>



-- 

DrMajorBob at bigfoot.com


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