Re: Default and head in function argument

*To*: mathgroup at smc.vnet.net*Subject*: [mg111643] Re: Default and head in function argument*From*: "Scot T. Martin" <smartin at seas.harvard.edu>*Date*: Sun, 8 Aug 2010 07:23:31 -0400 (EDT)

I believe that you're after: f[x:_Integer?(Positive):3] := x^3 The important point is the use of "(...)" to keep Mathematica oriented about your intentions. On Sat, 7 Aug 2010, NP wrote: > Hi, > > I know how to define a function so that it evaluates only when the > head of the argument is of a certain type: > > Clear[f]; > f[x_Integer?Positive] := x^3 > f[3] > f[3.1] > f[-3] > > 27 > f[3.1] > f[-3] > > and I also know how to set default to an argument of a function like > so: > > Clear[f] > f[x_:3] > f[] > > 27 > > How do I do both i.e., specify head and default value? > > Thanks, > > NP > >