Fwd: Re:Until -Reply -Reply
- To: mathgroup at smc.vnet.net
- Subject: [mg7263] Fwd: [mg7235] Re:[mg7063] Until -Reply -Reply
- From: BobHanlon at aol.com
- Date: Tue, 20 May 1997 02:59:06 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
The While[body; test] needs a semi-colon rather than a comma: n=10; While[(n=n-1)>5, Print[n]] 9 8 7 6 n=10; While[Print[n]; (n=n-1)>5] (* note semi-colon *) 10 9 8 7 6 Bob Hanlon --------------------- Forwarded message: From: sean at mail.creol.ucf.edu (Sean Ross) To: mathgroup at smc.vnet.net To: mathgroup at smc.vnet.net Sean: >The forms: >.....; or yours > Until[test_,body_]:=While[test=!=True,body]; >work fine, but are not a true Until because they don't execute body first. Mine is SetAttributes[Until,HoldAll] Until[test_, body_]:= While[body;test=!=True] and does execute body first: i=1;Until[True,i++];i 2 Am I missing something? Allan Hayes Thanks for the help. Your code does work and yes, you are missing something. As an "insider", you were aware of an undocumented While feature when I assumed that your While[body,test] was just a typo that I saw no need to quibble about. The mathematica book does not mention that While[test,body] evaluates test first, then body and While[body,test] does the reverse. I will promptly "Update" my personal copy of the mathematica book. This would probably make a nice addition to the list of revisions you are compiling somewhere.