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1

Let's say I have the following block of code:

x <- 0

while (x < 50)
 for (i in letters)
 print(i)
 x <- x + 10
 

What is the order of operations? Does the While stop criteria apply even if there are more loops in the for loop?

I tested this and it ran through the the whole for loop, despite x reaching 250.

Is there a way to add a rule that says follow the while loop before the for loop?

r

share|improve this question

asked Mar 25 at 5:03

CauderCauder

17411

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Related, is there a way to write a for loop that breaks any time the criteria is broken?
  
  – Cauder
  Mar 25 at 5:05
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Your for loop is nested inside the while loop; so the inner for loop finishes first, before returning to the outer while loop.
  
  – Maurits Evers
  Mar 25 at 5:11
  
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  The "priority" in this case is based on order: the while loop is executed first, then x is increased by 10 a total of 26 times before the while condition is re-evaluated. If you're asking if the while loop can interrupt the internal for loop, the answer is "no". If you need that, then for (i in letters) if (x >= 50) break; print(i); x <- x + 10; .
  
  – r2evans
  Mar 25 at 5:11
  
  

  
  
  
  

add a comment | 

1

Let's say I have the following block of code:

x <- 0

while (x < 50)
 for (i in letters)
 print(i)
 x <- x + 10
 

What is the order of operations? Does the While stop criteria apply even if there are more loops in the for loop?

I tested this and it ran through the the whole for loop, despite x reaching 250.

Is there a way to add a rule that says follow the while loop before the for loop?

r

share|improve this question

asked Mar 25 at 5:03

CauderCauder

17411

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Related, is there a way to write a for loop that breaks any time the criteria is broken?
  
  – Cauder
  Mar 25 at 5:05
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Your for loop is nested inside the while loop; so the inner for loop finishes first, before returning to the outer while loop.
  
  – Maurits Evers
  Mar 25 at 5:11
  
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  The "priority" in this case is based on order: the while loop is executed first, then x is increased by 10 a total of 26 times before the while condition is re-evaluated. If you're asking if the while loop can interrupt the internal for loop, the answer is "no". If you need that, then for (i in letters) if (x >= 50) break; print(i); x <- x + 10; .
  
  – r2evans
  Mar 25 at 5:11
  
  

  
  
  
  

add a comment | 

Let's say I have the following block of code:

x <- 0

while (x < 50)
 for (i in letters)
 print(i)
 x <- x + 10
 

What is the order of operations? Does the While stop criteria apply even if there are more loops in the for loop?

I tested this and it ran through the the whole for loop, despite x reaching 250.

Is there a way to add a rule that says follow the while loop before the for loop?

r

share|improve this question

asked Mar 25 at 5:03

CauderCauder

17411

x <- 0

while (x < 50)
 for (i in letters)
 print(i)
 x <- x + 10
 

share|improve this question

asked Mar 25 at 5:03

CauderCauder

17411

share|improve this question

asked Mar 25 at 5:03

CauderCauder

17411

asked Mar 25 at 5:03

CauderCauder

17411

asked Mar 25 at 5:03

CauderCauder

17411

2 Answers
2

active

oldest

votes

2

Your for loop is nested inside the while loop. Each time the while loop enters an iteration, control is handed over to its loop body which is the for loop in this case.The for loop then takes control and executes its iteration. After that, the for loop exits its control and hands over back to while loop. The while loop kind of decides the number of times the whole for loop executes.

To break a for loop when the criteria is broken or with any other logic, you can use a break statement inside an if block inside the loop body.

share|improve this answer

edited Mar 25 at 5:38

NelsonGon

5,64441135

answered Mar 25 at 5:31

lasith eshanlasith eshan

415

add a comment | 

1

Since (x < 50) is true at start, no more condition checking is done until for loop is completed. The only option is to use conditional break inside for loop.

for (i in letters)
 if (x < 50)
 break
 
 print(i)
 x <- x + 10

share|improve this answer

edited Mar 25 at 5:53

answered Mar 25 at 5:08

Suven PandeySuven Pandey

671216

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good answer overall but I think the if condition is around the wrong way.
  
  – Marius
  Mar 25 at 5:40
  

  
  
  
  

add a comment | 

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2

Your for loop is nested inside the while loop. Each time the while loop enters an iteration, control is handed over to its loop body which is the for loop in this case.The for loop then takes control and executes its iteration. After that, the for loop exits its control and hands over back to while loop. The while loop kind of decides the number of times the whole for loop executes.

To break a for loop when the criteria is broken or with any other logic, you can use a break statement inside an if block inside the loop body.

share|improve this answer

edited Mar 25 at 5:38

NelsonGon

5,64441135

answered Mar 25 at 5:31

lasith eshanlasith eshan

415

add a comment | 

2

Your for loop is nested inside the while loop. Each time the while loop enters an iteration, control is handed over to its loop body which is the for loop in this case.The for loop then takes control and executes its iteration. After that, the for loop exits its control and hands over back to while loop. The while loop kind of decides the number of times the whole for loop executes.

To break a for loop when the criteria is broken or with any other logic, you can use a break statement inside an if block inside the loop body.

share|improve this answer

edited Mar 25 at 5:38

NelsonGon

5,64441135

answered Mar 25 at 5:31

lasith eshanlasith eshan

415

add a comment | 

Your for loop is nested inside the while loop. Each time the while loop enters an iteration, control is handed over to its loop body which is the for loop in this case.The for loop then takes control and executes its iteration. After that, the for loop exits its control and hands over back to while loop. The while loop kind of decides the number of times the whole for loop executes.

To break a for loop when the criteria is broken or with any other logic, you can use a break statement inside an if block inside the loop body.

share|improve this answer

edited Mar 25 at 5:38

NelsonGon

5,64441135

answered Mar 25 at 5:31

lasith eshanlasith eshan

415

share|improve this answer

edited Mar 25 at 5:38

NelsonGon

5,64441135

answered Mar 25 at 5:31

lasith eshanlasith eshan

415

edited Mar 25 at 5:38

NelsonGon

5,64441135

edited Mar 25 at 5:38

NelsonGon

5,64441135

answered Mar 25 at 5:31

lasith eshanlasith eshan

415

answered Mar 25 at 5:31

lasith eshanlasith eshan

415

1

Since (x < 50) is true at start, no more condition checking is done until for loop is completed. The only option is to use conditional break inside for loop.

for (i in letters)
 if (x < 50)
 break
 
 print(i)
 x <- x + 10

share|improve this answer

edited Mar 25 at 5:53

answered Mar 25 at 5:08

Suven PandeySuven Pandey

671216

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good answer overall but I think the if condition is around the wrong way.
  
  – Marius
  Mar 25 at 5:40
  

  
  
  
  

add a comment | 

1

Since (x < 50) is true at start, no more condition checking is done until for loop is completed. The only option is to use conditional break inside for loop.

for (i in letters)
 if (x < 50)
 break
 
 print(i)
 x <- x + 10

share|improve this answer

edited Mar 25 at 5:53

answered Mar 25 at 5:08

Suven PandeySuven Pandey

671216

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good answer overall but I think the if condition is around the wrong way.
  
  – Marius
  Mar 25 at 5:40
  

  
  
  
  

add a comment | 

Since (x < 50) is true at start, no more condition checking is done until for loop is completed. The only option is to use conditional break inside for loop.

for (i in letters)
 if (x < 50)
 break
 
 print(i)
 x <- x + 10

share|improve this answer

edited Mar 25 at 5:53

answered Mar 25 at 5:08

Suven PandeySuven Pandey

671216

for (i in letters)
 if (x < 50)
 break
 
 print(i)
 x <- x + 10

share|improve this answer

edited Mar 25 at 5:53

answered Mar 25 at 5:08

Suven PandeySuven Pandey

671216

answered Mar 25 at 5:08

Suven PandeySuven Pandey

671216

answered Mar 25 at 5:08

Suven PandeySuven Pandey

671216