CS 421: Programming Languages and Compilers

Syllabus and Study Guide for Midterm 1

Studying for this exam


  • Understand the lecture slides and discussions thoroughly.
  • Revisit the MPs, MLs and WAs and make sure you understand the solutions thoroughly. Repeat any you are not comfortable with.
  • Take the pdf sample exam as a thorough overview for the actual exam.
  • Take the PrairieLearn Midterm1 Practice to be familiar with the precise nature of the questions and to see where you may have trouble taking the test in a timely enough manner.



The exam will cover the first 10 lectures, up to and including the lectures of Recursive Data Types in OCaml The following give examples of the kinds of questions you are likely to be asked for each topic:

  • Basic OCaml
    • Know the basic constructs (e.g., match, fun, let, let rec) like the back of your hand.
    • Be able to determine the type of OCaml expressions
    • Be able to evaluate OCaml expressions, both intuitively, and and step by step followong the steps discussed in class
    • Be able to describe the environment that results from a sequence of declarations
    • Be able to describe the closure that is the result of evalutating a function declaration
    • Understand what effect sequencing, function application and lambda lifting has on the order of evaluation of expressions
  • Recursion
    • Be able to write recursive functions, including (but not necessarily limited to) tail-recursive or forward recursive.
    • Be able to recognize whether a function is tail-recursive, and when a recursive call is in tail call position
  • Higher Order Functions (HOFs)
    • Be able to write the definitions of the common HOFs.
    • Be able to use map and fold to implement other functions, as in ML2.
    • Be able to write functions that use other functions as arguments
  • Continuations and Continuation Passing Style
    • Understand what the basic idea of what a continuation is.
    • Be able rewrite an operation / procedure in direct style to take a continuation to which to pass its results, while preserving the order of evaluation.
    • Be able to put a complex, possibly recursive procedure into full continutation passing style, while preserving the order of evaluation.
    • Be able to reproduce code for implementing giving the free varaibles in an expression and the CPS transformation of an expression, given the mathematical formulation of the cases for each of these.