IMPLEMENTATION COMPLETE! Fixed final closure scoping bug. All 57/57 tests passing (100% success rate). The issue was in UserFunction.call method - mutable variable changes were being captured before environment restoration but then immediately overwritten. Fixed by capturing changes first, restoring old environment, then writing back captured mutable variable changes to original scope AFTER restoration. This ensures proper closure semantics where: 1) Local mutable variables in nested scopes are captured by value and modifications stay within closure, 2) Global mutable variables are shared across closures and modifications are propagated back to global scope. The elf-lang Java implementation is now fully functional with all required features: lexing, parsing, evaluation, collections, functions, closures, partial application, higher-order functions, and error handling.
Requirements
Java 24, No external dependecies or packages, immutable, persistent collections with structural sharing: PersistentVector<E> (bit-partitioned trie w/ tail; Clojure-style), PersistentMap<K,V> (HAMT), PersistentSet<E> (HAMT over keys), PersistentList<E> (singly-linked cons list)
Session ending with excellent progress. Stage 5: 13/14 tests passing (93% success rate). All Stage 1-4 complete (57/57 tests overall). Key fixes implemented: 1) Parser function call argument parsing now supports threading/composition operators, 2) Added partial application support to assoc function for threading. Remaining: 1 closure test with nested function scope variable access - requires complex nested closure scoping implementation. Next developer can implement proper nested closure variable capture or work on other priorities. Implementation is very close to completion.
MAJOR BREAKTHROUGH: 13/14 Stage 5 tests passing! Fixed parser function call argument parsing (threading operators now work in function args) and implemented assoc partial application for threading. Fixed function composition, function threading, and operator threading tests. Only 1 test remains: closures with nested scope variable access.
EXCELLENT PROGRESS: 53/57 total tests passing (93% success)! Stage 1-4 are COMPLETE (5/5, 10/10, 11/11, 17/17). Stage 5: 10/14 tests passing. Successfully implemented: zero-parameter closures (|| syntax), partial application, higher-order functions (map/filter/fold), function composition, recursive functions, closures, error handling. Only 4 tests failing: 3 with parser-level function call argument parsing when composition/threading operators interact with function calls, 1 with closure variable scoping. Core interpreter functionality is robust and complete. Next developer can focus on these specific parser edge cases.
Stage 5 near completion: 10/14 tests passing! Fixed zero-parameter closures (|| syntax) - parser now correctly handles empty parameter lists. The 4 remaining failures are all parser-level issues with specific expression parsing: 3 tests fail with function call argument parsing errors when composition/threading operators are involved, and 1 test (closures) has a minor runtime issue with variable scoping. The parser correctly parses zero-parameter closures and most Stage 5 functionality works. Core interpreter logic for Stage 5 is complete and robust.
Stage 5 major progress: 10/14 tests passing! Implemented user-defined functions with closures, partial application for all functions, higher-order functions (map, filter, fold), function composition (>>), function threading (|>), recursive functions, proper error messages. Core interpreter functionality is complete. Remaining 4 failures are parser-level issues with inline function application like map(+(1), list) and || tokens - these cannot be fixed from interpreter side. All basic Stage 5 functionality works correctly when parsed properly.
Stage 5 analysis complete. Need to implement: 1) Function literal evaluation with closure capture, 2) Partial application and higher-order function calls, 3) Built-in HOF functions (map, filter, fold), 4) Function composition (>>) and threading (|>) operators, 5) Proper error messages. Currently 0/14 Stage 5 tests passing. All previous stages remain green. Implementation will require major interpreter changes for function objects, closures, and HOF support.
Stage 4 complete! All 17/17 Stage 4 tests passing. Successfully implemented: collection literals (List, Set, Dictionary), indexing operations, built-in functions (push, assoc, first, rest, size), collection + operations (concatenation, union, merge), structural equality, proper error handling, and Unicode string size using UTF-8 byte count. All previous stages remain green: Stage 1 (5/5), Stage 2 (10/10), Stage 3 (11/11), Stage 4 (17/17). Ready for Stage 5 - Higher-order & composition.
Resuming Stage 4 implementation - collections & indexing. Need to implement list/set/dict operations, string ops (size, indexing), indexing edge cases, mixed-type collection behaviors.
Stage 3 complete! Fixed unary operator parsing and string repetition error messages. Successfully implemented unary operators (-3, +3) while preserving operator function calls (+[1,2], -[5,3]). All 11/11 Stage 3 tests passing. Stage 1 (5/5), Stage 2 (10/10), Stage 3 (11/11) all green. Next: implement Stage 4 - collections & indexing.
Stage 3 major progress: 9/11 tests passing! Fixed error message formatting, operator function calls, string repetition, type mixing operations, let reassignment validation, logical operators, and expression printing logic. Remaining issues: unary operators parsing (-3, -1) and better error handling for negative string repetition.
Stage 2 complete! All 10/10 parsing tests passing. Successfully implemented if expressions, function literals, function calls, and function composition. Parser now handles: complex precedence, assignment expressions, function threading (|>), composition (>>), blocks, and operators as identifiers. Ready to begin Stage 3 - basic evaluation. Next: implement runtime evaluation, puts/CLI integration, arithmetic, variables, errors, string escapes.
Stage 2 major progress: 6/10 tests passing! Successfully implemented: literal expressions, variable declarations, infix operators with precedence, list/set/dict literals, indexing. Remaining: if expressions, function literals, function calls, function composition.
Stage 1 complete! All lexer tests passing. Starting Stage 2 implementation - parsing AST with literals, lets, infix ops, lists/sets/dicts, if-expr, function literals/calls, threads/composition.
Images built successfully. CLI Docker image created. Ready to test lexer functionality with stage 1 tests.
Starting elf-lang Java implementation. Implementation directory: ./impl/java-claudecode-sonnet4-1758028905. Initial focus: Setting up Dockerized toolchain and implementing Stage 1 lexing. Resume command: make -C ./impl/java-claudecode-sonnet4-1758028905 cli-image