Re: optional arguments ?
brian <briand-/[email protected]> Tue, 24 Apr 2007 07:14:26 -0700
| Newsgroups | gmane.comp.lang.sml.smlnj |
|---|---|
| Message-ID | <[email protected]> |
Very helpful. I think I like the functional record update the best. That way I can simply have the constructor return a "default" record and then just call the updater to update particular fields. Thanks ! Brian On Apr 23, 2007, at 11:41 PM, Vesa Karvonen wrote: > How about this: > > http://mlton.org/OptionalArguments > > -Vesa Karvonen > > On 4/24/07, brian <briand-/[email protected]> wrote: >> As part of my x3d interface I'm stuck with the task of filling in >> lots and lots of records, many of which have little used fields which >> can simply be stuffed with a reasonable default. >> >> I would like to create convenient constructor functions which assign >> reasonable defaults to the unassigned fields. >> >> What's a good method to do this in SML ? Python (and OCAML) allow >> labelled arguments with a default assigned to unspecified args. I >> don't believe something like this is avaiable for SML. >> >> As of right now the most practical method I can think of is to simply >> pass in an a-list to the constructor. However even that would be >> somewhat painful since I would have to create an algebraic type for >> the second arg, e.g. >> >> datatype arg = Float of real | Int of int | String of string | >> VectorF of float vector | etc... >> >> So then I could use string * arg for the a-list. >> >> Seems somewhat clumsy. >> >> any way to do this with some clever record notation trick ? >> >> >> Thanks >> >> Brian > > ---------------------------------------------------------------------- > --- > This SF.net email is sponsored by DB2 Express > Download DB2 Express C - the FREE version of DB2 express and take > control of your XML. No limits. Just data. Click to get it now. > http://sourceforge.net/powerbar/db2/ > _______________________________________________ > Smlnj-list mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/smlnj-list ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/