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add decrement example to UntypedLambda

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pilfer-pandex 2019-09-28 22:47:20 -07:00
parent c966f98a0f
commit 7d4ab2ceb9
1 changed files with 5 additions and 1 deletions
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6
pkg/proto/lib/UntypedLambda.hs
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@ -3,7 +3,7 @@ module UntypedLambda where
import ClassyPrelude
import Bound
import Control.Monad.Writer
import Control.Monad.Writer hiding (fix)
import Data.Deriving (deriveEq1, deriveOrd1, deriveRead1, deriveShow1)
import qualified Data.Function as F
import Data.List (elemIndex)
@ -307,6 +307,10 @@ posIn i n
copy :: Ord a => Exp a -> Nock
copy = copyToNock . toCopy
-- | Decrements its argument.
decrement :: Exp String
decrement = lam "a" $ App (fix "f" $ lam "b" $ Ift (Eql (Var "a") (Suc (Var "b"))) (Var "b") (App (Var "f") (Suc (Var "b")))) (Atm 0)
-- x. y. x
-- old: [8 [1 0] [1 8 [1 0] [1 0 30] 0 1] 0 1]
-- =+ 0 =