Automate.hs

module Automate where

{- LIQUID "--automatic-instances=smtinstances" @-}
   
{-@ LIQUID "--automatic-instances=liquidinstances" @-}

import Language.Haskell.Liquid.ProofCombinators 


fibA :: Int -> Int 
{-@ axiomatize fibA @-}
{-@ fibA :: Nat -> Nat @-}
fibA i | i <= 1 = i
      | otherwise = fibA (i-1) + fibA (i-2)

-- fibUp :: Int -> Proof 
{- fibUp :: i:Nat -> {fibA i <= fibA (i+1)} @-}
-- fibUp i 
-- | i <= 2    = trivial
-- | otherwise = fibUp (i-1) &&& fibUp (i-2) *** QED 


fibUp :: Int -> Proof
{-@ fibUp :: i:Nat -> {fibA i <= fibA (i+1)} @-}
fibUp 0 = trivial *** QED
fibUp 1 = trivial *** QED
fibUp i = fibUp (i-1) &&& fibUp (i-2) *** QED 

{- prop :: () -> {fibA 30 == 832040 } @-}
-- prop :: () -> Proof 
-- prop _ = trivial