On Sun, Feb 19, 2012 at 02:03:51PM -0500, Hendrik Boom wrote: > On Sun, Feb 19, 2012 at 07:05:37AM -0600, Robby Findler wrote: > > On Sun, Feb 19, 2012 at 12:30 AM, Gary Baumgartner <g...@cs.toronto.edu> > > wrote: > > > On a more productive note: in Racket code I define and use 'implies' a > > > lot, > > > often conjoined, for predicates. It's mainly of declarative value, which > > > is > > > perhaps why it's uncommon in implementation despite how common it is in > > > specification. And for boolean expressions in general I also use > > > 'neither'. > > > Are these something that others [would] use and so could be added to > > > Racket's > > > library? > > > > Seems to me adding implies, nand, and nor to racket/bool is a good idea. > > > > Let me know if you disagree (and if you disagree after I've already > > committed, it is a simple thing to drop the commit or change it). > > The trouble is, I can never remember which of 'nand' and 'nor' is > which. Either of them could mean 'neither'. But I do know what > 'neither' means. > > -- hendrik
This is why I'd prefer 'neither', although I can remember and teach 'nor' as abbreviating 'neither-nor'. There's no common Natural Language equivalent to 'nand', and here's some quick searching for discussions of this: http://www.wolframscience.com/reference/notes/1173a http://www.unige.ch/lettres/linge/syntaxe/journal/Volume5/ggg5_Moeschler.pdf http://www.lotpublications.nl/publish/articles/001530/bookpart.pdf Whether one can train themselves to use and reason about 'nand' well is another story. I might start by writing it as 'nall', 'not-allof', '¬∀', '∃¬', 'some-not', etc, until internalizing its properties and patterns. Exceptions could be a common use: (when ; something fails (some-not «needed-expr» ...) (raise . _)) ____________________ Racket Users list: http://lists.racket-lang.org/users
