RE: Collecting multiple function arguments into a List?

*To*: mathgroup at smc.vnet.net*Subject*: [mg30536] RE: [mg30519] Collecting multiple function arguments into a List?*From*: "Harvey P. Dale" <hpd1 at nyu.edu>*Date*: Tue, 28 Aug 2001 04:54:40 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

You can refer to a term in a list by its index. For example, if vars = {x1, x2, x3, x4, x5, x6, x7, x8}, then vars[[2]] will produce x2. Thus, if you wish a function of x1, x2, and x4 to equal, for example, 2 x1 + 3 x2 - x4^2, you can define f1[varlist_]:=2 varlist[[1]]+3 varlist[[2]] - varlist[[4]]^2. Evaluating f1[vars] will then do what you wish. You can follow this same process for f2, f3, etc. Best, Harvey Professor Harvey P. Dale Director National Center on Philanthropy and the Law New York University School of Law Room 206A 110 West 3rd Street New York, N.Y. 10012-1074 -----Original Message----- From: aes [mailto:siegman at stanford.edu] To: mathgroup at smc.vnet.net Sent: Friday, August 24, 2001 8:58 PM To: mathgroup at smc.vnet.net Subject: [mg30519] Collecting multiple function arguments into a List? I have a problem with 8 input variables, call 'em x1, x2, ... , x8, and I want to define a bunch of functions (using :=, not =) that depend on various subsets of these variables, e.g. f1[ x1_, x2_, x4_] := << stuff involving x1, x2, x4 >> f2[ x1_, x3_] := << stuff involving x1 and x3 only >> f3[[x2_, x3_, x5_, x8_} := << stuff involving x2, x3, x5, x8 >> To minimize typing and bookkeeping I'd like to define a list of the input variables, e.g. vars = {x1, x2, x3, x4, x5, x6, x7, x8} and then write all the function definitions in the simplified syntax f1[vars_] := << same stuff as above >> f2[vars_] := << same stuff as above >> f3[vars_] := << same stuff as above >> Can I do this? What's the required syntax? vars = {x1, x2, x3 ...} ?? OR vars = {x1_, x2_, x3_} ?? fn[vars] := << >> ?? OR fn[vars_] := << >>?? Thanks, siegman at stanford.edu _____________________________________________________________________ This message has been checked for all known viruses by the MessageLabs Virus Scanning Service. For further information visit http://www.messagelabs.com/stats.asp