Inference Videos for CS 3520/6520

• Inference 1 — introduction (1:37)

  Introduction to type inference.

• Inference 2 — type inference (3:06)

  Basic type inference in action.

• Inference 3 — function calls (2:11)

  Type inference for function calls.

• Inference 4 — occurs check (1:43)

  Type inference needs to avoid creating cyclic type equivalences, which could otherwise happen for expressions that have no type.

• Inference 5 — unify! and resolve (1:17)

  The unify! function will replace any use of equal? in the type checker, and it needs a resolve helper function.

• Inference 6 — representing type variables (1:27)

  Representing type variables in our new, inferencing type checker.

• Inference 7 — unify! examples (5:36)

  Examples for the unify! function.

• Inference 8 — unification (4:06)

  Unification is the algorithm for assigning types to type variables. The unify! function will need to implement this algorithm.

• Inference 9 — unify! (3:46)

  Implementing unify!.

• Inference 10 — typecheck (2:41)

  Updating typecheck to use unify!. See infer-lambda.rkt.

• Inference 11 — reporting errors (0:59)

  Type errors with unification can’t point to one wrong expression, but they can report a mismatch and one or more relevant expressions.