User loginNavigation 
Expressing the Type of a While LoopThe Cat language has a primitive called while. The while construct takes two functions as argument, an invariant and a variant. Both functions consume the same number of elements from the stack. The variant (loop body) produces the same number and type of elements that it consumes. The invariant produces the same types as the variant, plus it leaves a boolean value on top of the stack. The while loop terminates when the evaluation of the invariant leaves the value false on top of the stack. The while loop pops the value false, before exiting. So the question is: how should one express this in the type system? Here is my current proposal: define while : ( a:A=any* variant:(b:A)>(c:A) invariant:(d:A)>(d:A continue:bool) ) > ( result:A ) What is good or bad about this notation? What other possibilities should I consider? By cdiggins at 20060806 16:19  LtU Forum  previous forum topic  next forum topic  other blogs  4925 reads

Browse archivesActive forum topics 
Recent comments
8 hours 15 min ago
15 hours 6 min ago
18 hours 34 min ago
19 hours 23 min ago
21 hours 31 min ago
1 day 12 hours ago
1 day 16 hours ago
5 days 24 sec ago
1 week 2 days ago
1 week 2 days ago