record SingleLinkedStack {n : Level } (a : Set n) : Set n where
  field
  top : Maybe (Element a)
open SingleLinkedStack

pushSingleLinkedStack : {n m : Level } {t : Set m } {Data : Set n} -> SingleLinkedStack Data -> Data -> (Code : SingleLinkedStack Data -> t) -> t
pushSingleLinkedStack stack datum next = next stack1
  where
    element = cons datum (top stack)
    stack1  = record {top = Just element}

-- Basic stack implementations are specifications of a Stack

singleLinkedStackSpec : {n m : Level } {t : Set m } {a : Set n} -> StackMethods {n} {m} a {t} (SingleLinkedStack a)
singleLinkedStackSpec = record {
                           push = pushSingleLinkedStack
                         ; pop  = popSingleLinkedStack
                         ; get  = getSingleLinkedStack
                         }

createSingleLinkedStack : {n m : Level } {t : Set m } {a : Set n} -> Stack {n} {m} a {t} (SingleLinkedStack a)
createSingleLinkedStack = record {
                        stack = emptySingleLinkedStack ;
                        tackMethods = singleLinkedStackSpec
                        }