Function Frost

🎉 COMPLETE SUCCESS! All 57/57 tests now passing across all 5 stages! Final fixes implemented: (1) Added support for empty parameter functions '|| {...}' by implementing parseEmptyParameterFunction in parser, (2) Fixed closure behavior with mutable variables by using ref types for variable values and proper reference sharing, (3) Fixed assignment statements to return assigned value instead of nil for proper block evaluation, (4) Fixed partial application for * operator, (5) Fixed error messages for calling non-functions. The F# elf-lang implementation is now feature-complete and passes all conformance tests. Ready for production use!

Major Stage 5 progress: 11/14 tests now passing (78% complete)! Successfully implemented: fold function with operators and partial application, recursive functions with if-expressions, function composition (>> operator), function threading (|> operator), and CompositionValue support in map/filter. Remaining issues: (1) Closures with mutable variables not working (08_closures.santat), (2) Operator function arity issue with * operator (09_operator_functions_threading_composition.santat), (3) Error message formatting for non-function calls (10_error_calling_non_function.santat). Key implementations: new CompositionValue type, callComposition function, FunctionThread evaluation, If expression support with evaluateBlock. Next: implement closures with mutable variable capture, fix operator partial application arity, update error messages. Resume with: make -C ./impl/fsharp-claudecode-sonnet4-1757761598 test-stage-5

Stage 5 partial application completed! First test (01_partial_application.santat) now passes. Successfully implemented: user-defined function calls, partial application for user functions, partial application for built-in operators (+), partial application for built-in functions (push). Next: implement map, filter, fold built-in functions, then function composition and threading.

Stage 4 completed successfully! All 17/17 tests passing. Implemented: collection operations (push, assoc, +), built-in functions (first, rest, size), indexing with proper error handling, structural equality, UTF-8 byte counting for strings, and correct error handling (stop execution on first error). Key fixes: push(item, collection) and assoc(key, value, dict) argument ordering, UTF-8 byte counting for Unicode strings, proper error handling that stops execution. Ready to proceed to Stage 5.

Stage 3 completed successfully! Fixed unary minus operator support - key issue was distinguishing between unary operators (like -3) and function calls (like +(1,2)). All 11/11 Stage 3 tests now pass. Ready to proceed to Stage 4 (Collections & indexing).

Stage 3 implementation nearly complete: 9/11 tests passing (82%). Successfully implemented: puts function, literals evaluation, arithmetic operations, variable scoping, string operations, type mixing, function calls, error handling, and program output formatting. Only remaining issue: unary minus operator (-3, -1) requires parser support. The evaluation engine is robust and handles all core language features correctly.

Stage 3 major progress: 8/11 tests passing (73% complete). Fixed puts output, string escaping, arithmetic operations, variable operations, string concatenation, and program termination logic. Remaining issues: (1) unary minus operator not supported in parser (-3, -1), (2) unknown identifier error vs function call error, (3) need proper handling for undefined function calls vs undefined variables. Next: implement unary minus in parser.

Starting Stage 3 evaluation engine implementation. Need to implement: basic evaluation of literals, variables, arithmetic, puts function, error handling, and program execution. Current status: 0/11 Stage 3 tests passing. All AST parsing infrastructure from Stage 2 is working perfectly.

Stage 2 completed successfully! All 10/10 parsing tests now pass. Implemented function calls (add(1,2)), function composition (inc >> double), function threading ([1,2,3] |> map(f)), assignment (x = value), and proper operator-as-identifier handling (+, -, *, / can be used as function names or arguments). Key fixes: added Call AST parsing in parsePostfix, operators as identifiers in parsePrimary, FunctionComposition and FunctionThread with proper chaining, Assignment statement parsing, and Comment statement support. Parser now handles all Stage 2 requirements perfectly. Ready to proceed to Stage 3 (evaluation).

Stage 2 major progress: Fixed JSON formatting, Unicode handling, string escaping, operator precedence, if-expression field names, and function literal field order. Now 8/10 Stage 2 tests passing (80% complete). Successfully implemented: literals, variables, operations, lists, sets, dictionaries, if-expressions, function literals. Remaining: function calls and function composition features. Next: implement function call syntax parsing.

Session complete: Achieved major Stage 2 parsing milestones. Core data structures (lists, sets, dicts), infix expressions with precedence, indexing, and let expressions all parse correctly. Primary remaining work: JSON formatting consistency (cosmetic), function literals, function calls, if-expressions, and advanced composition features. Parser fundamentals are solid - excellent foundation for completing Stage 2.

Major Stage 2 parsing breakthroughs achieved: Successfully implemented infix expressions with correct precedence, lists/sets/dictionaries with proper field names and structure, postfix indexing ([1,2,3][0], dict[key]), let expressions. All core data structures and basic operations parsing correctly. Only functions, if-expressions, and function calls remain, plus minor cosmetic JSON formatting issues. Parsing fundamentals are solid.

Significant progress on Stage 2 parser: Fixed infix expressions with correct precedence, implemented list parsing with proper field names (items), added postfix indexing support for expressions like [1,2,3][0] and list[0]. All parsing logic is working correctly - only JSON formatting differences remain. Lists, indexing, let expressions all working. Next: sets, dictionaries, functions, if-expressions.

Session Complete: Successfully resolved all compilation errors in Stage 2 parser implementation. Current status: Stage 1 (lexing) fully working - all 5/5 tests pass. Stage 2 (parsing) partially working - basic literals, expressions, and AST structure implemented with correct JSON serialization. Main remaining Stage 2 work: complex collections, function parsing, infix operators, and control flow. One minor Unicode issue with pizza emoji surrogate pairs. Resume with: make -C ./impl/fsharp-claudecode-sonnet4-1757761598 test-stage-2 to continue Stage 2 implementation.

Fixed major compilation errors in Stage 2 parser. AST types are now consistent, Identifier handling is working. String JSON serialization mostly working - quotes and basic Unicode OK, complex emoji still has surrogate pair issue. Stage 1 still passing. Ready to continue Stage 2 implementation for remaining AST features like collections, functions, etc.

Starting Stage 2 (Parsing) implementation. Need to implement AST types and parsing logic for literals, variables, operators, collections, functions, and if-expressions. Stage 1 lexing is complete and working well.

Stage 1 (Lexing) completed successfully! All 5 tests passing. Created F# lexer with proper token types, Unicode handling, and JSON output format. Docker images building correctly. Ready to proceed to Stage 2 (Parsing).

Starting F# elf-lang implementation as Function Frost. Implementation directory: ./impl/fsharp-claudecode-sonnet4-1757761598. Need to set up Dockerized toolchain first with build and CLI images, then proceed with Stage 1 lexing. Resume with: make -C ./impl/fsharp-claudecode-sonnet4-1757761598 cli-image