[R] how does while work

[Liaw, Andy]

What he wanted is a mechanism to "watch" for a condition on a variable, and
stop execution as soon as that condition is TRUE, regardless of where in the
program.  The only thing that I know of that sort of does this is inside
gdb, the GNU debugger.  AFAIK this is impossible.  If anyone has better
idea, I'd like to hear about it, too.

Andy

> -----Original Message-----
> From: David A Richmond [mailto:richmond at saintmarys.edu]
> Sent: Thursday, March 21, 2002 11:00 AM
> To: jimi adams
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] how does while work
> 
> 
> On Wed, 20 Mar 2002, jimi adams wrote:
> 
> > i am having some problems with a program that i am writing 
> and i think that
> > knowing how the while command works will help me to figure 
> out where i am
> > going wrong
> > *when do you get kicked out of a while loop?*
> > (i.e., in the following example  what would the final value 
> of 'a' be?) i
> > thought it would be 99 but running it in R i get 101 (and 
> 101 for x too!)
> > 
> > while (x <100) {
> >   for (i in 1:101) {
> >     i -> x
> >     x -> a
> >   }
> > *here*  
> > }
> 
> Essentially the while condition doesn't get checked until 
> just before the
> last curly brace (where I inserted *here* above), so the for 
> loop gets to
> do it's thing until i (and x and a) reach 101 and only then 
> is the while
> condition allowed to drop you out of the loop.
> 
> > while this is a crude example, it is the basic form of what 
> i am trying to
> > do, and i am guessing that while is not what i am looking for...
> 
> what exactly are you trying to do?
> 
> daver
> 
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