← Applied intuition Interview Insights

Applied intuition·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say
Apr 2026

Summary

Applied Intuition had me build a mini compiler from scratch during what felt like a very long technical screen. The scope was broader than I expected and covered way more ground than a typical coding question.

Questions Asked (1)

Q1

Implement a mini compiler or interpreter for a small language, covering tokenization, parsing into an AST, and evaluation of constructs like variable assignment, arithmetic, conditionals, and possibly function calls. Also discuss your grammar design, error handling strategy, and how you'd extend the language.

System DesignTechnical Trade-offsAlgorithms & Data Structures
Author's notes

This was a lot.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the scope and requirements of the mini language, then walk through the classic compiler pipeline: tokenizer, parser, and evaluator. Emphasize clean separation of concerns, robust error handling, and extensibility, and be prepared to discuss trade-offs in grammar design and implementation choices.

Pro tip: Demonstrate a working knowledge of recursive descent parsing and the visitor pattern for AST evaluation, as these are industry-standard techniques that show you understand both theory and practical implementation.

1. Clarify Requirements and Scope

Ask questions to understand the expected language features, performance constraints, and error handling needs. Define the minimal viable language and plan for extensibility.

2. Design the Grammar and Tokenizer

Specify the grammar (e.g., using EBNF) and implement a tokenizer that converts source code into a stream of tokens. Discuss handling of whitespace, comments, and literals.

3. Implement the Parser and AST

Build a recursive descent parser that consumes tokens and produces an Abstract Syntax Tree (AST). Explain how to handle operator precedence and associativity.

4. Implement the Evaluator

Traverse the AST to evaluate expressions, manage variable environments, and implement control flow (conditionals, loops) and function calls. Discuss scoping and recursion.

5. Discuss Error Handling and Extensions

Describe strategies for lexical, syntactic, and semantic errors (e.g., error recovery, informative messages). Outline how to extend the language with new features like types or modules.

Key Points to Mention

  • Tokenization: regular expressions or hand-written scanner, token types, and handling of literals and identifiers.
  • Parsing: recursive descent, operator precedence (e.g., Pratt parsing), and AST node design.
  • Evaluation: environment/scope management, variable assignment, arithmetic operations, and control flow.
  • Error handling: panic mode recovery, error messages with line/column info, and semantic checks.
  • Extensibility: modular design, plugin architecture for new syntax, and potential for bytecode compilation.
  • Trade-offs: simplicity vs. performance, interpreted vs. compiled, and static vs. dynamic typing.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.