Re: Mathematica question (another one)

*To*: mathgroup at smc.vnet.net*Subject*: [mg5751] Re: [mg5737] Mathematica question (another one)*From*: Allan Hayes <hay at haystack.demon.co.uk>*Date*: Tue, 14 Jan 1997 10:42:29 -0500*Sender*: owner-wri-mathgroup at wolfram.com

Gadi Oron <oron at tremois.pmmh.espci.fr> [mg5737] Mathematica question (another one) writes >>>>>>>>>>> >How should i define a function that has an optional argument with >certain form, let me explain: >Suppose that a function has to receive an OPTIONAL list of rules >that takes the deafault value {}. > >I've tried : > >func[sub:{___Rule}:{}]:=... > >But it does not work. Gadi: f[Optional[sub:{___Rule} ,{}]]:= A[sub] is OK on V3.0 but not on V2.2. However f[sub:{___Rule}:{}]:= A[sub] is not accepted as proper input in V3.0 and, does not work in V2.2. You might like to try ___?OptionQ instead of ___Rule. ?OptionQ OptionQ[e] returns True if e can be considered an option or list of options, and False otherwise. Allan Hayes hay at haystack.demon.co.uk http://haystack.demon.co.uk