Algebraic Data Types + Pattern Matching = Elegant and readable Java code
summary
Builds a working cryptarithmetic solver for SEND + MORE = MONEY using Java’s Project Amber features, implementing expressions as a sealed Expression hierarchy and evaluation via a pattern-matching switch. Uses records and sealed interfaces for product/sum types, a DFS generator to reduce ~90 million raw combinations to ~181,000 constrained combos, and checks constraints (unique-values, equality) with expression evaluation. The unit test runs and finds a valid assignment; source code is on GitHub. record deconstruction and guarded patterns
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chapters (21)
- 0:00Introduction
- 0:45Outline
- 1:19Questions
- 1:38Puzzle
- 2:31Rules
- 4:22Problem Analysis
- 5:20Constraint Programming
- 6:00Solution Design
- 7:16Expression Evaluation
- 9:03Algebraic Data Types
- 9:27Product Types
- 10:12Sum Types
- 11:02Pattern Matching
- 11:27Instance of
- 12:41Switch
- 13:40Primitive Types in Patterns
- 14:19Solving the Problem
- 15:34Implementation
- 17:09Seal Interface
- 23:16Generator
- 23:50Puzzle constraint
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