CSC362L01 2004S, Lab 9: Type Checking

Admin:
* Happy April Fools' day
* Missing: Angela, Piper, Shihan (excused), Ananta (excused)

Overview:
* Goals of today's lab
* Lab
* Reflection

What should/could the type checker check/do? (Types and variables)
* Are variables declared? (Checked)
* Are variables redeclared? (Checked)
* Where are variables declared? [NO: Syntactic]
* Are variables initialized? (Not yet checked)
* Do operands to operations have the right types? (Partially checked)
  * Addition: int x int or real x real
  * Modulo: int x int
  * Etc.
* Does the RHS of an assignment have the same type as the LHS (Checked)
* We might have the type checker coerce types (Not done)

What were the "significant bugs" in compound expressions?
* "difine" is misseppelled [No]
* / is not set to return real in all cases
* typeCheck(1 < 3): Returns integer as a type
* Permits true < false
* Generally: Does not validate operands and use different return type
  (Incorrect assumption: The return type is the same as the parameter type)