More Loops

Skipping index

You can skip an index using the word +LOOP 

			: skip5 25 0 do  i . 5 +LOOP ; 
			skip5
should display 
0 5 10 15 20 ok

Note that 25 is not printed, even though it equals to the end index.
However, if the skip is negative, i.e., counting down. You get the end index. 

			: skip5down 0 25 do i . -5 +loop ;
			skip5down
should display 
25 20 15 10 5 0	 ok

Stopping a DO...LOOP

To stop a 
DO
 loop use the words 
LEAVE
 and 
UNLOOP
:
		
    
		
  1. LEAVE
     simply leaves the loop, and executing continues after LOOP
    2. 
		
  2. The pair 
    UNLOOP EXIT
     must be used if you want to exit the word completely.
    3. 
		

	
 
	
Some examples:

		
			: short 
				100 0 do  
					i dup . 2 = if LEAVE then 
				loop 
				"Hello!" . 
			;
	
			short
		

		will display 
0 1 2 Hello! ok

	

		Another example: 
		
			: never-ever 
				100 0 do 
					i dup . 
					2 = if UNLOOP exit then 
				loop 
				"I will never be printed!" . ;
				
			never-ever
		
will only print 
0 1 2 ok

	
	
	
	
Be sure you try out these examples and thoroughly understand them before moving on!

	
	
Quiz

	
	
Question 1

	
What do you think would happen if we changed the 100 0 in 
SHORT
 to 100 2 ? Try to guess the answer then experiment with the Smojo Terminal.

	
	
	


		

	
Question 2

	
What do you think would happen if we changed the LOOP in 
NEVER-EVER
 to 5 +LOOP ? Guess the answer then check with the Terminal.

	
	
	


	
 
Next: Other Looping Constructs