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how does while work

4 messages · jimi adams, Giovanni Petris, Greg Snow +1 more

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jimi adams
# 
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
  }
}

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...

jimi adams
Department of Sociology
The Ohio State University
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Giovanni Petris
# 
assuming you enter the while loop with a value of x less than 100, 
the for loop sets, in its last iteration, a=x=101 (which is the last
value `i' takes). at this point you also exit the while loop, since
x<100 is false.

Giovanni

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Greg Snow
    

    

      
      #
    

  


  

      
On Wed, 20 Mar 2002, jimi adams wrote:

        

            

      
      
      
    

        
If you are trying to jump out of a for loop early then try something like:

for (i in 1:101) {
  i -> x
  if (! x<100 ) { break }
  x -> a
}

the "next" command will also skip the rest of the body of the loop and
start on the next iteration.

Hope this helps,

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      David A Richmond
    

    

      
      #
    

  


  

      
On Wed, 20 Mar 2002, jimi adams wrote:

        

            

      
      
      
    

        
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.

            

      
      
      
    

        
what exactly are you trying to do?

daver

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