Calculator in Rust

What you'll build

We will build a full-featured command-line calculator in Rust from scratch. Starting with a minimal REPL, we will gradually add a tokenizer that splits expressions into meaningful tokens, implement the shunting-yard algorithm to convert infix notation to reverse Polish notation, and assemble a stack-based evaluator that calculates the final result.

Along the way, we will practice idiomatic Rust patterns: custom error types with Display, the Result/? pipeline, newtype wrappers, trait implementations (FromStr, Add, Sub, Mul, Div), and test-driven development. By the end, the calculator will handle parenthesized expressions with correct operator precedence, decimal numbers, and clear error messages for invalid input.

Learning objectives

✓Build an interactive REPL with careful input/output handling

✓Implement an arithmetic expression tokenizer

✓Convert infix notation to RPN using the shunting-yard algorithm

✓Evaluate RPN expressions using a stack

✓Design a reliable error-handling pipeline with custom error types

✓Apply the newtype pattern together with trait implementations

Prerequisites

▸Basic Rust syntax (functions, enums, structs)

▸Familiarity with pattern matching and the Result type

▸Understanding of basic arithmetic and operator precedence

Course curriculum

1 Interactive Shell

—Project scaffold

—Read Loop

—Shell Commands

2 The calculate Function and Tokenizer

—Entry Point

—Tokenizer Scaffold

—CalcError Error Type

3 Parsing Numbers

—Number Collector

—Tests and Fractional Numbers

4 Tokens

—Type for a Token

—Tokenization Test

5 Operators

—Operator Token

—The Operator Type

—Unary Minus

6 Parentheses

—Parenthesis Tokens

—Tracking Context

7 Shunting-Yard Algorithm

—Conversion Scaffold

—Operator Precedence

—Closing Parentheses

—Final Parentheses Checks

8 Stack-Based Evaluation

—Evaluator Scaffold

—Stack Operations

—Evaluation Errors

—Unary Minus in the Evaluator

Technologies

Rust Calculator Shunting-yard algorithm Reverse Polish notation Tokenizer REPL Error handling Newtype pattern

FAQ

Is this a video course?

No. You work through the project step by step in your browser, and the reference code for each step saves to your disk — yours to run and keep locally.

Do I need to install anything?

No. The playground runs entirely in your browser — no toolchain or local setup required.

Can I try it before subscribing?

Yes. Preview steps are available without a subscription so you can see the format and quality first.

What do I get with full access?

Every step unlocked, the Workbench app, a snapshot for each step, jump-to-any-step navigation, and all new playground releases.

Does it work with an AI agent like Claude or Codex?

Yes. You can work through a playground solo or alongside an AI agent.

Is there reference code?

Yes. Every step has a complete reference solution you can compare against.