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 8 lectures, up to and including the lecture on Forward and Tail Recursion. 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 following 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 (function expression) 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, fold_right, fold_left and map.
    • Be able to use map and fold to implement other functions, as in MP3.
    • Be able to write functions that use other functions as arguments