To run BNFC:

  bnfc -m Calc.cf
  make

To run the interpreter:

  echo "1+2*3" | runhaskell icalc.hs

To run the compiler:

  echo "1+2*3" | runhaskell ccalc.hs
  java Foo

Hand-written files:

  Calc.cf              -- bnfc grammar
  Interpreter.hs       -- interpreter definition
  CodeGenerator.hs     -- code generator definition
  icalc.hs             -- interpreter main function
  ccalc.hs             -- code generator main function

BNFC-generated files:

  AbsCalc.hs           -- abstract syntax
  LexCalc.hs           -- lexer generated by Alex
  LexCalc.x            -- lexer source for Alex
  ParCalc.hs           -- parser generated by Happy
  ParCalc.y            -- parser source for Happy
  PrintCalc.hs         -- printer (from abstract syntax to strings)
  SkeletonCalc.hs      -- skeleton for pattern matching