Interpreters

Q1: REPL

Notes for Academic Interns: Ask the student the following: Explain REPL. What are the different stages and what is done in each stage?

Solution:

1. Read

   • Calls lexer, which breaks input into tokens.
   • Calls parser, which organizes the tokens into data structures.

2. Eval

   • Mutual recursion between eval and apply. eval evaluates expressions (through lookups or by recursively calling eval and apply).
   • apply applies an evaluated operator to its evaluated operands

3. Print

   • Display the result of evaluating user input

4. Loop

   • Repeat if there are more expressions to interpret.