152 def lexing(r: Rexp, s: String) : Val = lex(r, s.toList)

   152 def lexing(r: Rexp, s: String) : Val = lex(r, s.toList)

   153 

   153 

   154 lexing(("ab" | "ab") ~ ("b" | EMPTY), "ab")

   154 lexing(("ab" | "ab") ~ ("b" | EMPTY), "ab")

   155 

   155 

   156 lexing(OPT("ab"), "ab")

   156 lexing(OPT("ab"), "ab")

   157 

   160 

   158 // some "rectification" functions for simplification

   161 // some "rectification" functions for simplification

   159 def F_ID(v: Val): Val = v

   162 def F_ID(v: Val): Val = v

   160 def F_RIGHT(f: Val => Val) = (v:Val) => Right(f(v))

   163 def F_RIGHT(f: Val => Val) = (v:Val) => Right(f(v))

   161 def F_LEFT(f: Val => Val) = (v:Val) => Left(f(v))

   164 def F_LEFT(f: Val => Val) = (v:Val) => Left(f(v))