blob: df933a43efd698c9263d32485d02b8f88f14ebf0 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
module Minilang.Lambda.EvalSpec (spec) where
import Control.Concurrent (threadDelay)
import Control.Concurrent.Async (race_)
import Minilang.Lambda.Eval (Term (..), eval, evalNeed)
import Test.Hspec (Spec, describe, it, shouldBe)
spec :: Spec
spec = do
let fix = Lam "x" (App (Var "x") (Var "x"))
let omega = App fix fix
let term = App (App (Lam "x" (Lam "y" (Var "y"))) omega) (Var "z")
describe "call-by-value eval" $ do
it "evaluates 'x' as itself" $ do
let term = Var "x"
eval term [] `shouldBe` Var "x"
it "evaluates '((λ x. x) y)' as 'y'" $ do
let term = App (Lam "x" (Var "x")) (Var "y")
eval term [] `shouldBe` Var "y"
it "evaluates '((λ x y. y) y z t)' as '(z t)'" $ do
let snd' = Lam "x" (Lam "y" (Var "y"))
let term = App (App (App snd' (Var "y")) (Var "z")) (Var "t")
eval term [] `shouldBe` App (Var "z") (Var "t")
it "diverges on evaluating argument bound to ω" $
shouldDiverge $ eval term []
describe "call-by-need eval" $ do
it "evaluates 'x' as itself" $ do
evalNeed (Var "x") [] `shouldBe` Var "x"
it "evaluates '(λ x y . y) ⊥ z' as 'z'" $ do
evalNeed term [] `shouldBe` Var "z"
it "diverges on evaluating ω" $
shouldDiverge $ evalNeed omega []
shouldDiverge :: Term -> IO ()
shouldDiverge t =
race_
(t `seq` fail "Did not diverge")
(threadDelay 1000000)
|
