For-Loop loops

[bigyihsuan]

A for loop would be nice. Do-while is implemented as |a|(code)ʌʟ|a| and while as ʌʟ|b||a|(code)ʟ|a||b|. For loops are complex currently, and a Forth-like do ... loop would simplify things.

Close-mid to open front vowels are available. Open vowels available.

For-Loop

• FOR: ɑ (end start -- ). Pops 2 for index bounds. Loop jumps back to here+1 if index < end.
• GETIDX: e ( -- index). Pushes the current loop's index. NOP if not in a loop.
• SETIDX: ø (value -- ) Sets the current loop's index to value.
• LOOP: ɒ ( -- ). If index < limit, jump to associated For. Else, continue.
• EXIT: ε ( -- ). Discards the current loop's data from the loop stack, and exits the loop.

  Implementation Thoughts

• 2 new Lex tokens FOR/LOOPSTART and LOOPEND
• LOOP always after FOR
• How to keep track of the index? (loop stack) [1]
• What about nesting? (loop stack) [1]
• FOR pushes end and start onto the loop stack. start becomes index. L( -- end index)
• EXIT should pop and discard 2 values from the loop stack, and jump to just after the next LOOP. `L(end index -- )

Uses

• Easy counting loops, so less label spaghetti
• Loops == "easier" to follow code
• LOOP doesn't increment, so can use math ops and SETIDX to do custom IDX incrementation (i+=2, multiplication, division, etc)
• IDX is always less than limit, but going negative can be done with INV.
• More?

  Things to do

• [x] Implementation
• [x] Testing
• [x] Update Esolangs page

[1]: see https://stackoverflow.com/questions/6949434/how-to-implement-loop-in-a-forth-like-language-interpreter-written-in-c

[bigyihsuan]

Finished loops with commit cbd1bf4.