004_loop_simple.md

Example 004 - Loop Simple

This shows a very simple way how to loop in DominoScript by moving back the instruction pointer to the start of the loop.

Opcodes:

• NUM 0—1
• STR 0—2
• DUPE 0—3
• SUB 1—1
• BRANCH 4—1
• NUMOUT 5—1
• STROUT 5—3
• NOOP 6—6

Pseudocode:

Before the loop we push a number to the stack to act as index. Each iteration we print the index and decrement it. When the index reaches 0, the BRANCH instruction will eventually break out of the loop.

• NUM 48
• LOOP_START:
  • DUPE
  • NUMOUT
  • STR '\n' STROUT
  • DUPE
  • NUM 1SUB
  • DUPE
  • BRANCH
    • true: NOOP until Instruction Pointer is back at LOOP_START
    • false: Continue after LOOP_END
• LOOP_END
• STR 'DONE' STROUT

DominoScript:

. 0 . . . . . . . . . . . . . . . . . . . . . . . . . . .
  |                                                      
. 1 . . 6 6—6 6—6 6—6 6—6 6—6 6—6 6—6 6—6 6—6 6—6 6—6 6 .
        |                                             |  
. 1 . . 6 . . . . . . . . . . . . . . . . . . . . . . 6 .
  |                                                      
. 0 6—6 0—3 5—1 0—2 1—0 1—3 0—0 5—3 0—1 0—1 1—1 0—3 4—1 .
                                                         
. . . . . . . . . . . . . . . . . . . . . . . . . . . 0 .
                                                      |  
. . . . . . . . 5 0—0 6—2 1—1 1—4 1—1 2—4 1—1 5—2 1—1 2 .
                |                                        
. . . . . . . . 3 . . . . . . . . . . . . . . . . . . . .

Notes:

This way of looping can waste a few instruction cycles depending on how many NOOPs are executed to move the IP back to the start again.

You can obviously lay the dominos out in a way where the start and end are closer together, and avoid the need for NOOPs altogether BUT maybe you like placing sequences of dominos in a certain way and don't want to change that.

In that case, take a look at the next example that uses the JUMP instruction to move the IP back to the start instead of NOOPs.