Do fish have legs: Language design for the commercial coder
summary
Builds a small DSL in Scala for backend search queries, implements an AST, a runtime evaluator and a static typechecker that rejects impossible queries like "fish has legs", and demos it working. Shows concrete rules: record and union types, subtyping, and branch-aware type refinement for if expressions. Implementation totals about 200 lines of Scala with a roughly 10-line evaluator, uses Scala for function dispatch, and successfully types and runs the example queries.
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chapters (10)
- 0:00Start
- 2:20Problem
- 7:04Evaluation
- 8:34Apply case
- 14:18Types
- 14:39Simplest type system
- 15:02Symbol case
- 15:58Restrictive type systems
- 16:59Rule 1 (revised)
- 18:09Further complications
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