Re: How can I parse arguments of an expression unevaluated?

*To*: mathgroup at smc.vnet.net*Subject*: [mg100953] Re: [mg100894] How can I parse arguments of an expression unevaluated?*From*: Carl Woll <carlw at wolfram.com>*Date*: Thu, 18 Jun 2009 20:46:11 -0400 (EDT)*References*: <200906180848.EAA19681@smc.vnet.net>

Erich Neuwirth wrote: > What I would like to have is the following: > I want to give the expression > MyFunArgs[1, 2, a = 3, b = 4] > and I would like to get 3 lists, > the first list has all the arguments which are > not written as an assignment, {1,2} > The second list should be a list of strings > with the names of the variables to be assignes > {"a","b"} > and the third list should be the values to be assigned: > {3,4} > > so > MyFunArgs[1, 2, a = 3, b = 4] > should produce > {{1,2},{"a","b"},{3,4}} > > How can I accomplish this? > > > Here's one way: In[911]:= SetAttributes[MyFunArgs, HoldAll] MyFunArgs[a__] := {Cases[Hold[a], Except[_Set]], Cases[Hold[a], HoldPattern[Set[lhs_, _]] :> SymbolName[Unevaluated[lhs]]], Cases[Hold[a], HoldPattern[Set[_, rhs_]] :> rhs]} In[913]:= MyFunArgs[1, 2, a = 3, b = 4] Out[913]= {{1, 2}, {"a", "b"}, {3, 4}} Carl Woll Wolfram Research

**References**:**How can I parse arguments of an expression unevaluated?***From:*Erich Neuwirth <erich.neuwirth@univie.ac.at>