nested loops are broken

[skx]

We use the stack, secretly, to implement do and while, for our loops.

This works (also in word-definitions):

10 0 do dup . loop

But the following fails:

10 0 do dup .  10 0 do dup .  loop loop

This is surprising since the stack should allow nesting properly, but still .. This should be fixed.

• NOTE: Defining a loop in a word, then calling that in a loop works, which reinforces my point that the stack should be OK:

     > : foo 10 0 do dup 48 + emit loop cr ;
     > 10 0 do foo loop 
     > 0123456789
     > 0123456789
     > 0123456789
     > 0123456789
     > 0123456789
     > 0123456789
     > 0123456789
     > 0123456789
     > 0123456789
     > 0123456789

[skx]

• Define a new Loop structure ("cur" + "max")
• When DO is compiled add that to e.loops
  • immediately emit "-6 NN" - where "-6" is "do-loop"
  • Add a jump if-failed to LOOP+1
• Compile the body.
• When LOOP is emitted jump back to DO+1
• LOOP+1 will pop the Loop entry off the stack.

Nothing gets stored on the stack. We'll have to define i to get the current iteration, of course..

[skx]

Fixing this would also increase our test-coverage - perhaps to exceed 99% :)