; ---------- SORTS --------------------

( deftype X STR )
;---------------------

( deftype Stack LIST X )
;---------------------
; ---------- STATE --------------------

( def _state
  ( quote S )
)
;---------------------
; ---------- FUNCTIONS ----------------

( def _ops
  ( plus _ops
    ( makeff
      (
        ( quote push )
        ( quote
          (
            (
              ( X )
              ( Stack )
            )
            ( Stack )
          )
        )
      )
    )
  )
)
;---------------------

( def push lambda
  ( x s )
  ( cons x s )
)
;---------------------

( def _ops
  ( plus _ops
    ( makeff
      (
        ( quote top )
        ( quote
          (
            (
              ( Stack )
            )
            ( X )
          )
        )
      )
    )
  )
)
;---------------------

( def top lambda
  ( s )
  ( if
    ( nequal s
      ( makeseq )
    )
    ( head s )
    ( strcat "ERROR (precondition violated) in function " "top" )
  )
)
;---------------------

( def _ops
  ( plus _ops
    ( makeff
      (
        ( quote pop )
        ( quote
          (
            (
              ( Stack )
            )
            ( Stack )
          )
        )
      )
    )
  )
)
;---------------------

( def pop lambda
  ( s )
  ( if
    ( nequal s
      ( makeseq )
    )
    ( tail s )
    ( strcat "ERROR (precondition violated) in function " "pop" )
  )
)
;---------------------
; ---------- EVENTS -------------------

( def _ops
  ( plus _ops
    ( makeff
      (
        ( quote INIT )
        ( quote
          (
            ( ) NIL
          )
        )
      )
    )
  )
)
;---------------------

( def INIT lambda
  ( )
  ( def S
    ( makeseq )
  )
)
;---------------------

( def _ops
  ( plus _ops
    ( makeff
      (
        ( quote PUSH )
        ( quote
          (
            (
              ( X )
            ) NIL
          )
        )
      )
    )
  )
)
;---------------------

( def PUSH lambda
  ( x )
  ( def S
    ( push x S )
  )
)
;---------------------

( def _ops
  ( plus _ops
    ( makeff
      (
        ( quote POP )
        ( quote
          (
            ( )
            ( X )
          )
        )
      )
    )
  )
)
;---------------------

( def POP lambda
  ( )
  ( if
    ( nequal S
      ( makeseq )
    )
    ( prog1
      ( head S )
      ( def S
        ( tail S )
      )
    )
    ( strcat "ERROR (precondition violated) in function " "POP" )
  )
)
;---------------------

( def _ops
  ( plus _ops
    ( makeff
      (
        ( quote TOP )
        ( quote
          (
            ( )
            ( X )
          )
        )
      )
    )
  )
)
;---------------------

( def TOP lambda
  ( )
  ( if
    ( nequal S
      ( makeseq )
    )
    ( head S )
    ( strcat "ERROR (precondition violated) in function " "TOP" )
  )
)
;---------------------