I went straight for the direct-execution approach, just parsing each line and dispatching on the command name.
Start by clarifying the language specification: command syntax, variable scoping, error handling, and output format. Then design a simple interpreter loop that parses each command, executes it against a key-value store, and collects output. Discuss trade-offs between a quick-and-dirty implementation and a more extensible design, and walk through an example to validate correctness.
Pro tip: Demonstrate production-quality thinking by discussing how you would handle edge cases like undefined variables, type mismatches, and malformed commands, and how you'd structure the code for easy extension with new commands.
Ask about the exact command syntax, variable types, error handling expectations, and output format. Confirm whether the interpreter should be a one-pass executor or support control flow.
Outline a simple architecture: a parser to tokenize commands, an executor with a dispatch mechanism (e.g., switch or command pattern), and a variable store (e.g., hash map). Mention extensibility for new commands.
Write pseudocode or actual code for SET, ADD, and PRINT, including validation for undefined variables, type checking, and malformed input. Decide on error reporting (e.g., exceptions vs. error messages).
Walk through a sample command sequence, showing the state of the variable store and output. Test edge cases like adding to an undefined variable, printing an unset variable, and invalid commands.
Talk about design trade-offs: simplicity vs. extensibility, performance considerations, and how you might add features like loops, conditionals, or functions. Mention testing strategies.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
This is where the conversation got interesting.
Start by outlining the core architectural changes needed: adding an environment chain for scoping, an AST or bytecode representation for control flow, and a call stack for functions. Then explain how each feature (variables, IF, WHILE, CALL/RETURN) maps onto these components, emphasizing trade-offs between simplicity and performance. Conclude by discussing testing and incremental implementation.
Pro tip: Mention that you would first extend the parser to produce an AST, then implement a tree-walking interpreter with an environment chain, and only later consider bytecode compilation for performance—this shows you understand the evolution from simple to optimized interpreters.
Modify the grammar to recognize variable declarations, IF/WHILE statements, and CALL/RETURN expressions. Build an abstract syntax tree (AST) that represents these constructs hierarchically.
Introduce an environment chain (or scope stack) where each environment maps variable names to values. For blocks, create child environments that inherit from parents, enabling lexical scoping and closures.
For IF, evaluate the condition and execute the appropriate branch. For WHILE, repeatedly evaluate the condition and execute the body until false. Ensure proper handling of break/continue if needed.
Use a call stack to manage function invocations. When CALL is evaluated, create a new environment for the function's parameters and local variables, execute the body, and return the result. RETURN unwinds the call stack and passes the value back.
Compare tree-walking vs. bytecode compilation, environment chain vs. flat arrays, and recursion vs. explicit stack. Mention potential optimizations like tail-call elimination or just-in-time compilation.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.