Re: Optional Alternatives

*To*: mathgroup at smc.vnet.net*Subject*: [mg50036] Re: Optional Alternatives*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Thu, 12 Aug 2004 05:44:00 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

On 8/11/04 at 5:53 AM, sh2.7183 at misspelled.erthlink.net (Selwyn Hollis) wrote: >Is it possible to require a function argument to match alternative >patterns and be optional at the same time? As a toy example, >suppose I define >f[x:_Real|_Rational]:= x The only way I know to achieve this is as follows: f[x_Real]:=x f[x_Rational:=x >Is there a way make the argument optional with a given default >value, say 0? I've tried this: >f[Optional[x:_Real|_Rational, 0]]:= x The following might do for you In[1]:= g[x_, s_:0] := x + s In[2]:= g[2] Out[2]= 2 In[3]:= g[2, 2] Out[3]= 4 -- To reply via email subtract one hundred and four