Assignment #4
ECEN 5023, CSCI 7135
Due May 6, 2008
1. Implement in OCaml a type checker and interpreter for a language with
the following features:
•Booleans and natural numbers (Figures 8-1 and 8-2).
•First-class functions (lambdas) (Figure 9-1). The type annotations
on function parameters are optional, so if they are left off you should
infer their types in your inference algorithm.
•References (Figure 13-1)
•Records (Figure 11-7) and variants (Figure 11-11).
2. Add support for two or more of the following options (your choice):
•Let-polymorphism and type inference (described in Section 22.7 of
the text). Do not use term substitution to implement let-polymorphism
in the type inference algorithm. Instead use the more efficient ap-
proach described on the bottom of page 333.
•recursive types
•first-class polymorphism
•subtyping, subsumption, and bounded polymorphism
3. Write a type checker and interpreter for the simply typed lambda calculus
in this language that you’ve implemented.
4. Bonus: if you’ve implemented recursive types and bounded polymor-
phism, then you can implement the object encoding of Abadi, Cardelli,
and Viswanathan in their paper “An interpretation of objects and object
types”.
A few remarks:
•You may use any of the implementations on the web page of the textbook
as your starting point.
•Use the exact syntax that is used in the textbook.
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