import "Prelude"

gSum :: Additive a => [a] -> <Proc> a
gSum list = getRef answer
  where
    answer = ref zero
    
    constraint El a
    
    ?x <- list => El ?x
    -El ?x, -El ?y => El (?x + ?y)
    El ?x => answer := ?x
    
main = (gSum [1,6,9], gSum [1.0,6.0,9.0]) 
--
(16,16.0)
--
import "StandardLibrary"

topologicalSort :: [(a,a)] -> <Proc> [a]
topologicalSort dependencies = MList.freeze answer
  where
    answer = MList.create ()
    
    (?x,?y) <- dependencies           =>  Dep ?x ?y, InDegree ?x 0, InDegree ?y 1
    -InDegree ?x ?a, -InDegree ?x ?b  =>  InDegree ?x (?a + ?b)
    InDegree ?x 0                     =>  AdjustInDegrees ?x, MList.add answer ?x
    AdjustInDegrees ?x, Dep ?x ?y     =>  InDegree ?y (-1)
    
main = topologicalSort [(2,4),(3,7),(7,2),(1,3)]
--
[1, 3, 7, 2, 4]
--
import "StandardLibrary"

topologicalSort :: Show a => [(a,a)] -> <Proc> [a]
topologicalSort dependencies = MList.freeze answer
  where
    answer = MList.create ()
    
    -Candidate ?x, Candidate ?x  =>  True
    (?x,?y) <- dependencies      =>  Dep ?x ?y, Candidate ?x
    -Candidate ?x, Dep _ ?x      =>  True
    Candidate ?x                 =>  MList.add answer ?x 
    Candidate ?x, -Dep ?x ?y     =>  Candidate ?y

main = topologicalSort [(2,4),(3,7),(7,2),(1,3)]
--
[1, 3, 7, 2, 4]