--- From maude docs

--- This is a comment.
*** This is a comment too.

fmod SIMPLE-NAT is
  sort Nat .
  op zero : -> Nat .
  op s_ : Nat -> Nat .
  op _+_ : Nat Nat -> Nat .
  
  
  --- variables
  vars N M : Nat .
  
  --- rewrite rules
  eq zero + N = N .
  eq s N + M = s (N + M) .
endfm