# Completed Features

## v0.2.1 (2025-01-16)

### Lambda Expressions ✅
- **Lambda Expression Parsing**
  - Modified: `src/frontend/parser.rs`, `src/frontend/ast.rs`
  - Parse `|params| body` syntax for anonymous functions
  - Support empty params `||`, single `|x|`, and multiple `|x, y|`
  - Support typed parameters `|x: i32, y: f64|`
  - Handle `||` token ambiguity (OrOr vs empty lambda)
  - Completed: 2025-01-16

- **Lambda Type Inference**
  - Modified: `src/middleend/infer.rs`
  - Extended Algorithm W for lambda expressions
  - Automatic parameter type inference
  - Function type construction for lambdas
  - Completed: 2025-01-16

- **Lambda Transpilation**
  - Modified: `src/backend/transpiler.rs`
  - Transpile to Rust closures with correct syntax
  - Preserve parameter names
  - Type inference delegation to rustc
  - Completed: 2025-01-16

- **Lambda Test Coverage**
  - Added comprehensive tests in parser, transpiler, and type inference
  - Test empty params, single param, multiple params, typed params
  - Test lambda in let bindings and function calls
  - All 172 tests passing
  - Completed: 2025-01-16

## v0.2.0 (2025-01-16)

### Type System Implementation ✅
- **Type Inference Engine (Algorithm W)**
  - Created: `src/middleend/infer.rs`
  - Complete Hindley-Milner type inference
  - Automatic type inference for all expressions
  - Support for polymorphic types and type schemes
  - Completed: 2025-01-16

- **Unification Engine**
  - Created: `src/middleend/unify.rs`
  - Unification with occurs check
  - Prevents infinite types
  - Proper error handling for type mismatches
  - Completed: 2025-01-16

- **Type Environment**
  - Created: `src/middleend/environment.rs`
  - Binding and scheme management
  - Standard library functions included
  - Generalization and instantiation support
  - Completed: 2025-01-16

- **Type Annotations Parsing**
  - Modified: `src/frontend/parser.rs`
  - Parse `: Type` and `-> Type` annotations
  - Optional type annotations (defaults to 'Any')
  - Gradual typing support
  - Completed: 2025-01-16

### Language Features ✅
- **Method Call Syntax**
  - Modified: `src/frontend/parser.rs`, `src/backend/transpiler.rs`
  - Parse `x.method(args)` with dot operator
  - Method chaining support
  - Type inference for built-in methods (len, push, pop, chars)
  - Transpiles to Rust method calls
  - Completed: 2025-01-16

- **String Interpolation**
  - Modified: `src/backend/transpiler.rs`
  - Support for `{variable}` in strings
  - Transpiles to Rust's `format!` macro
  - Works with println! and other formatting functions
  - Completed: 2025-01-15

### Parser Improvements ✅
- **Multi-statement Programs**
  - Modified: `src/frontend/parser.rs`
  - Proper block handling
  - Optional semicolons
  - Completed: 2025-01-15

- **Import System**
  - Modified: `src/frontend/parser.rs`
  - Complex paths with `::`
  - Braced imports like `use std::io::{Read, Write}`
  - Completed: 2025-01-15

- **Expression vs Statement Handling**
  - Modified: `src/runtime/repl.rs`
  - REPL correctly evaluates expressions vs statements
  - Proper result printing for expressions
  - Completed: 2025-01-15

### Documentation ✅
- **README Updates**
  - Updated feature list
  - Added implementation status section
  - Updated examples
  - Completed: 2025-01-16

- **CHANGELOG**
  - Created comprehensive v0.2.0 release notes
  - Documented all features and improvements
  - Completed: 2025-01-16

- **API Documentation**
  - Updated `src/lib.rs` with new examples
  - Added type inference examples
  - Added method call examples
  - Completed: 2025-01-16

- **Example Files**
  - Created `examples/type_inference.ruchy`
  - Created `examples/method_calls.ruchy`
  - Completed: 2025-01-16

## v0.1.0 (2025-01-15)

### Core Language ✅
- Basic lexer and parser
- AST representation
- Transpilation to Rust
- Interactive REPL
- Pipeline operators
- Pattern matching (basic)
- For loops and ranges
- List literals
- If/else expressions
- Let bindings
- Function definitions

### Quality ✅
- Zero SATD policy established
- PMAT integration
- 146 initial tests
- Property-based testing framework
- Benchmark suite