6.1.1800
LOOP
 
CORE
Interpretation:
Interpretation semantics for this word are undefined.

Compilation:
( C: do-sys -- )

Append the run-time semantics given below to the current definition. Resolve the destination of all unresolved occurrences of LEAVE between the location given by do-sys and the next location for a transfer of control, to execute the words following the LOOP.

Run-time:
( -- ) ( R: loop-sys1 -- | loop-sys2 )

An ambiguous condition exists if the loop control parameters are unavailable. Add one to the loop index. If the loop index is then equal to the loop limit, discard the loop parameters and continue execution immediately following the loop. Otherwise continue execution at the beginning of the loop.

See:
6.1.1240 DO, 6.1.1680 I, 6.1.1760 LEAVEA.6.1.1800 LOOP.

Rationale:
Typical use:

   : X ... limit first DO ... LOOP ... ;

or

   : X ... limit first ?DO ... LOOP ... ;

Testing:
T{ : GD1 DO I LOOP ; -> }T
T{          4        1 GD1 ->  1 2 3   }T
T{          2       -1 GD1 -> -1 0 1   }T
T{ MID-UINT+1 MID-UINT GD1 -> MID-UINT }T