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Orderless attribute for named functions and function arguments
*To*: mathgroup at smc.vnet.net
*Subject*: [mg72525] Orderless attribute for named functions and function arguments
*From*: "Hannes Kessler" <HannesKessler at hushmail.com>
*Date*: Thu, 4 Jan 2007 07:04:24 -0500 (EST)
Dear experts,
a way to use the attibute Orderless that works for functions with named
arguments in the form of rules is
SetAttributes[f,Orderless];
f[
"Named argument 1" -> x_,
"Named argument 2" -> y_,
"Named argument 3" -> z_]:=
Module[{xx, yy, zz},
{xx, yy, zz} = {x, y, z};
(*Do something with xx, yy, zz and return the result*)
...];
Calling the function with arguments in different ways gives identical
results.
No need to care about the order of the named arguments:
f1 = f[
"Named argument 1" -> 1,
"Named argument 2" -> 2,
"Named argument 3" -> 3];
f2 = f[
"Named argument 2" -> 2,
"Named argument 1" -> 1,
"Named argument 3" -> 3];
f1 == f2
--> True
Now I want an additional dependence of the result on a name of the
function in the following form:
f[functionName_String][
"Named argument 1" -> x_,
"Named argument 2" -> y_,
"Named argument 3" -> z_]:=
Module[{xx, yy, zz},
{xx, yy, zz} = {x, y, z};
(*Do something with xx, yy, zz*)
...;
(*Return the result depending on functionName*)
Which[
MatchQ[functionName, "func1"], value1,
MatchQ[functionName, "func2"], value2,
...]];
However, it is not possible anymore to assign the attribute Orderless
as
SetAttributes[f[functionName_String],Orderless];
generates an error message:
SetAttributes::sym: Argument f[functionName_String] at position 1 is
expected \
to be a symbol.
A simple solution is to reverse the definition of f:
SetAttributes[f,Orderless];
f[
"Named argument 1" -> x_,
"Named argument 2" -> y_,
"Named argument 3" -> z_][functionName_String]:=...
Is there another way to reach the same goal? Reversing the definition
of f is of course completely acceptable in most cases. Nevertheless, in
some cases it may preferrable to view f[functionName] as different
functions specified by the string functionName, and the arguments to
these functions should be given in any order.
Thanks in advance,
Hannes Kessler
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