RE: function definition
- To: mathgroup at christensen.cybernetics.net
- Subject: RE: function definition
- From: Chip Sample <sample at shire.ac.arknet.edu>
- Date: Fri, 21 Oct 1994 09:52:25 CDT
Can anyone explain the principle for function definition that yields the following: First define f2[x]: in: f2[x_] := x + 2; in: ?f2 out: Global`f2 f2[x_] := x + 2 Now re-define f2[x], and we see that the old definition has been overwritten: in: f2[x_] := x + 3; in: ?f2 out: Global`f2 f2[x_] := x + 3 But now define f2[y], and see that the old definition is the one that is used by Mma! in: f2[y_] := y + 4; out: ?f2 Global`f2 f2[x_] := x + 3 f2[y_] := y + 4 Check out values of f2. They're all from the x + 3 definition: in: f2[x] out: 3 + x in: f2[y] out: 3 + y in: f2[1] out: 4 _____________________________/________________________________________________ David Kramer Telephone: (717) 291-4339 Coordinator of Academic Computing e-mail: D_Kramer at Acad.FandM.edu Franklin & Marshall College FAX: (717) 399-4446 Lancaster, Pennsylvania 17604-3003 USA _______________________________________________________________________\______ +++++++++++++++++++++++++++++++++++++++++++++++++++ I call that a bug. Clearly Mma uses the first definition it finds it its list, but I think the second definition should over write the first. The only thing I could think was that if before f2[x_] was defined, x was declared an integer (say), and before f2[y_] was defined, y was declared a vector, then f2 could be used to do different things depending on the data type it is sent. BUT THIS DOESN'T WORK. So I think its a bug. Chip