Type 3

1 DO reference =
2+ ,
2 %specification

specification:

1 exp1
2? 
2 TO exp2
2.1? BY exp3
2 BY exp3
2.1? TO exp2
2 REPEAT exp6
3? 
3 WHILE ( exp4 )
3.1? UNTIL ( exp5 )
3 UNTIL ( exp5 )
3.1? WHILE ( exp4 )