../neo/neo YOU: read ONLY docs files and update project README.md
1: read ONLY docs files and update project README.md - IN PROGRESS assistant false -- AGENT START WORKING 1 --- STOP_REASON: tool_use AI:
I'll start by reading the docs directory and the current README.md to understand what we're working with. CALLING TOOL: dir_list {"name":"docs"} $$$ {"entries":[{"name":"design.md","is_dir":false},{"name":"plan.md","is_dir":false},{"name":"plan_02.md","is_dir":false}]}
!!!!! {"command":"test -f README.md && echo "EXISTS" || echo "NOT FOUND""}: OK CALLING TOOL: bash_command {"command":"test -f README.md && echo "EXISTS" || echo "NOT FOUND""} $$$ "EXISTS\n"
--- STOP_REASON: tool_use CALLING TOOL: file_read {"path":"docs/design.md"} $$$ "# Math Expression Evaluator — Design Document\n\n## Requirements Summary\n- Language: Go\n- Operators: +, -, *, / with parentheses\n- Numbers: floating point (e.g. 3.14, 42, 0.5)\n- Functions: user-defined with f(x) = x + 1 syntax\n- Interface: CLI REPL\n- Error handling: print error message, continue REPL\n\n### Function Definition Requirements\n- Syntax: f(x) = x + 1 — name, parenthesized params, =, body expression\n- Multiple params: f(x, y) = x + y\n- Function calls: Allowed anywhere a number can appear; arguments are arbitrary expressions\n- Persistence: Definitions persist across REPL lines\n- Cross-calling: Functions can call other user-defined functions (late binding)\n- Built-ins: None\n- Redefinition: Not allowed (error)\n- Output on define: Print "defined \u003cname\u003e"\n\n## Approaches Considered\n\n### 1. Recursive-Descent with AST (chosen)\n- Lexer → Parser → AST → Evaluator → REPL\n- Clean separation: each stage is independently testable\n- AST is a reusable intermediate representation\n- Easy to extend (new operators, pretty-printing, optimization)\n- Well-suited for 2 precedence levels + parentheses\n\n### 2. Recursive-Descent with Direct Evaluation\n- Parser evaluates inline — no AST\n- Fewer types, less code\n- Couples parsing and evaluation — harder to test, extend\n\n### 3. Shunting-Yard Algorithm\n- Converts to RPN then evaluates\n- Good for many precedence levels; overkill here\n- Harder to produce clear error messages\n\nDecision: Approach 1. The AST adds minimal overhead but provides clean boundaries.\n\n## Architecture\n\n\nInput string\n │\n ▼\n ┌───────┐\n │ Lexer │ string → []Token\n └───┬───┘\n │\n ▼\n ┌────────┐\n │ Parser │ []Token → Statement (ExprStmt | FuncDef)\n └───┬────┘\n │\n ▼\n ┌───────────┐\n │ Evaluator │ stateful: function registry + expression evaluation\n └───┬───────┘\n │\n ▼\n ┌──────┐\n │ REPL │ read line → parse → route (define or eval) → print\n └──────┘\n\n\n## Component Interfaces\n\n### Token (data type)\n\ngo\npackage token\n\ntype Type int\n\nconst (\n Number Type = iota // numeric literal\n Plus // +\n Minus // -\n Star // *\n Slash // /\n LParen // (\n RParen // )\n Ident // identifier (e.g. f, x, myFunc)\n Comma // ,\n Equals // =\n EOF // end of input\n)\n\ntype Token struct {\n Type Type\n Literal string // raw text, e.g. \"3.14\", \"+\", \"f\"\n Pos int // position in input (for error messages)\n}\n\n\n### Lexer\n\ngo\npackage lexer\n\n// Tokenize converts an input string into a slice of tokens.\n// Returns an error if the input contains invalid characters.\n// Recognizes: numbers, operators, parens, identifiers, comma, equals.\nfunc Tokenize(input string) ([]token.Token, error)\n\n\n### AST (data types)\n\ngo\npackage ast\n\n// Node is the interface all expression AST nodes implement.\ntype Node interface {\n node() // sealed marker method\n}\n\n// NumberLit represents a numeric literal.\ntype NumberLit struct {\n Value float64\n}\n\n// BinaryExpr represents a binary operation (e.g. 1 + 2).\ntype BinaryExpr struct {\n Op token.Type // Plus, Minus, Star, Slash\n Left Node\n Right Node\n}\n\n// Ident represents a variable reference (function parameter).\ntype Ident struct {\n Name string\n}\n\n// FuncCall represents a function call (e.g. f(1+2, 3)).\ntype FuncCall struct {\n Name string\n Args []Node\n}\n\n// Statement is the interface for top-level parsed constructs.\ntype Statement interface {\n stmt() // sealed marker method\n}\n\n// ExprStmt wraps an expression used as a statement.\ntype ExprStmt struct {\n Expr Node\n}\n\n// FuncDef represents a function definition: name(params) = body\ntype FuncDef struct {\n Name string\n Params []string\n Body Node\n}\n\n\n### Parser\n\ngo\npackage parser\n\n// Parse converts a slice of tokens into an expression AST.\n// Kept for backward compatibility.\nfunc Parse(tokens []token.Token) (ast.Node, error)\n\n// ParseLine converts a slice of tokens into a Statement.\n// Distinguishes function definitions from expressions.\nfunc ParseLine(tokens []token.Token) (ast.Statement, error)\n\n\nGrammar (extended):\n\nline → funcdef | expr\nfuncdef → IDENT '(' params ')' '=' expr\nparams → IDENT (',' IDENT)*\nexpr → term (('+' | '-') term)*\nterm → factor (('*' | '/') factor)*\nfactor → NUMBER | IDENT '(' args ')' | IDENT | '(' expr ')'\nargs → expr (',' expr)*\n\n\nDefinition detection: Scan token stream for Equals token. If present → parse as function definition. If absent → parse as expression. This works because = is not valid in expressions.\n\n### Evaluator\n\ngo\npackage evaluator\n\n// Evaluator holds function definitions and evaluates expressions.\ntype Evaluator struct {\n funcs map[string]*ast.FuncDef\n}\n\n// New creates a new Evaluator with an empty function registry.\nfunc New() *Evaluator\n\n// Define registers a function definition.\n// Returns an error if a function with the same name is already defined.\nfunc (e *Evaluator) Define(def *ast.FuncDef) error\n\n// Eval evaluates an expression AST node.\n// env provides variable bindings (function parameters).\n// Pass nil for top-level evaluation.\nfunc (e *Evaluator) Eval(node ast.Node, env map[string]float64) (float64, error)\n\n\nFunction call evaluation:\n1. Look up function name in registry\n2. Evaluate each argument expression in caller's environment\n3. Check argument count matches parameter count\n4. Create new environment: param[i] → argValue[i]\n5. Evaluate function body in new environment\n\nLate binding: Function body references are resolved at call time, not definition time. This naturally supports cross-function calls as long as the called function is defined before the call is evaluated.\n\n### REPL\n\ngo\npackage repl\n\n// Run starts the read-eval-print loop, reading from r and writing to w.\n// Maintains function registry across lines.\nfunc Run(r io.Reader, w io.Writer)\n\n\nLine processing flow:\n1. Tokenize line\n2. ParseLine() → Statement\n3. Switch on statement type:\n - *ast.FuncDef → evaluator.Define(def), print "defined \u003cname\u003e"\n - *ast.ExprStmt → evaluator.Eval(expr, nil), print result\n\n## Package Layout\n\n\nmatheval/\n├── cmd/\n│ └── matheval/\n│ └── main.go # entry point, calls repl.Run\n├── token/\n│ └── token.go # Token type and constants\n├── lexer/\n│ ├── lexer.go # Tokenize function\n│ └── lexer_test.go\n├── ast/\n│ └── ast.go # AST node types + Statement types\n├── parser/\n│ ├── parser.go # Parse + ParseLine functions\n│ └── parser_test.go\n├── evaluator/\n│ ├── evaluator.go # Evaluator struct with Define + Eval\n│ └── evaluator_test.go\n├── repl/\n│ ├── repl.go # REPL loop with state\n│ └── repl_test.go\n├── docs/\n│ ├── design.md\n│ └── plan.md\n├── go.mod\n└── README.md\n\n\n## Error Handling\n- Lexer: returns error for invalid characters (e.g. @, #)\n- Parser: returns error for syntax errors (unexpected token, mismatched parens, malformed definitions)\n- Evaluator: returns error for division by zero, undefined function, undefined variable, argument count mismatch, function redefinition\n- REPL: catches any error, prints it, prompts for next input\n\n## Key Design Decisions\n1. Statement vs Node separation — Statement interface separates top-level constructs (definitions vs expressions) from expression nodes. This keeps the expression evaluator clean.\n2. Stateful Evaluator struct — replaces the previous stateless Eval() function. Required to hold the function registry. The Eval method still takes an explicit environment for testability.\n3. Late binding — function bodies reference other functions by name; resolved at call time. Simple and correct.\n4. Backward-compatible Parse() — existing Parse() function kept. New ParseLine() added for the REPL.\n5. Sealed AST interface — unexported marker method prevents external implementations, keeping the node set closed.\n6. Position tracking in tokens — enables precise error messages.\n7. REPL takes io.Reader/io.Writer — makes it testable without stdin/stdout.\n8. Definition detection via Equals scan — simple and unambiguous since = cannot appear in expressions.\n"
CALLING TOOL: file_read {"path":"docs/plan.md"} $$$ "# Math Expression Evaluator — Implementation Plan\n\n## Phase: Implement\n\nSteps are ordered. Each step includes writing the code and its unit tests (TDD).\n\n### Step 1: Project Skeleton\n- go mod init matheval\n- Create directory structure: cmd/matheval/, token/, lexer/, ast/, parser/, evaluator/, repl/\n- Create placeholder main.go\n\n### Step 2: Token Package\n- Define Type enum constants\n- Define Token struct\n- Add String() method on Type for debugging\n\n### Step 3: Lexer\n- Implement Tokenize(input string) ([]Token, error)\n- Handle: whitespace skipping, number literals (integers and decimals), operators +-*/, parentheses (), EOF, invalid characters\n- Tests: valid expressions, decimal numbers, invalid chars, empty input, whitespace-only\n\n### Step 4: AST Package\n- Define Node interface with sealed marker\n- Define NumberLit struct\n- Define BinaryExpr struct\n\n### Step 5: Parser\n- Implement recursive-descent parser following grammar:\n - expr → term (('+' | '-') term)*\n - term → factor (('*' | '/') factor)*\n - factor → NUMBER | '(' expr ')'\n- Internal parser struct to track position in token slice\n- Return error on: unexpected token, mismatched parens, trailing tokens\n- Tests: single number, simple binary, precedence, parentheses, nested parens, error cases\n\n### Step 6: Evaluator\n- Implement Eval(node ast.Node) (float64, error)\n- Recursively walk AST\n- Return error on division by zero\n- Tests: literals, all 4 operators, nested expressions, division by zero\n\n### Step 7: REPL\n- Implement Run(r io.Reader, w io.Writer)\n- Read line, tokenize, parse, evaluate, print result or error\n- Loop until EOF\n- Tests: successful expression, error expression, multi-line session\n\n### Step 8: main.go\n- Wire repl.Run(os.Stdin, os.Stdout)\n\n### Step 9: Integration Test\n- End-to-end test: feed expression string through all stages, verify result\n- Test edge cases: deeply nested parens, long expressions\n\n### Step 10: Final Commit \u0026 README\n- Write README.md with usage instructions\n- Final commit\n"
CALLING TOOL: file_read {"path":"docs/plan_02.md"} $$$ "# Implementation Plan: Function Definitions\n\n## Overview\nBottom-up implementation through the stack: token → ast → lexer → parser → evaluator → repl → integration tests. Each step maintains backward compatibility and follows TDD.\n\n## Steps\n\n### Step 1: Token layer (token/token.go)\n- Add Ident, Comma, Equals constants to Type enum\n- Update String() for new types\n- No tests needed — pure data types\n\n### Step 2: AST layer (ast/ast.go)\n- Add Ident struct: Name string; implements Node\n- Add FuncCall struct: Name string, Args []Node; implements Node\n- Add Statement interface with sealed stmt() marker\n- Add ExprStmt struct: Expr Node; implements Statement\n- Add FuncDef struct: Name string, Params []string, Body Node; implements Statement\n- No tests needed — pure data types\n\n### Step 3: Lexer (lexer/lexer.go)\n- Add isLetter(ch byte) bool helper\n- Before the single-char switch, add branch: if isLetter(ch), scan identifier (letter then letters/digits), emit Ident token\n- Add ',' → Comma and '=' → Equals to single-char switch\n- Tests: identifiers (x, foo, f1), comma, equals, full definition f(x) = x + 1, call f(1, 2), mixed with numbers\n\n### Step 4: Parser (parser/parser.go)\n- Extend factor():\n - Ident followed by LParen → parse FuncCall: consume (, parse args as comma-separated exprs, consume )\n - Ident not followed by LParen → return \u0026ast.Ident{Name}\n- Add parseFuncDef(): expects Ident( params ) = expr\n- Add ParseLine(tokens) (Statement, error):\n - Scan for Equals token (not inside parens)\n - If found → parseFuncDef() → *ast.FuncDef\n - If not → expr() → *ast.ExprStmt{Expr}\n- Keep Parse() unchanged for backward compat\n- Tests: ParseLine for defs and exprs, factor for ident and func call, error cases\n\n### Step 5: Evaluator (evaluator/evaluator.go)\n- Add Evaluator struct with funcs map[string]*ast.FuncDef\n- New() *Evaluator\n- Define(def *ast.FuncDef) error — error on redefinition\n- Eval(node ast.Node, env map[string]float64) (float64, error):\n - *ast.NumberLit → return value\n - *ast.BinaryExpr → recurse left/right with same env\n - *ast.Ident → lookup in env, error if not found\n - *ast.FuncCall → lookup func, eval args in caller env, bind params, eval body in new env\n- Keep package-level Eval(node) (float64, error) as backward-compat wrapper\n- Tests: all existing tests still pass, new tests for Ident, FuncCall, Define, errors\n\n### Step 6: REPL (repl/repl.go)\n- In Run(): create evaluator.New() before loop\n- Replace evalLine() with inline logic using ParseLine()\n- *ast.FuncDef → ev.Define(def), print \"defined \u003cname\u003e\"\n- *ast.ExprStmt → ev.Eval(stmt.Expr, nil), print result\n- Tests: define + call across lines, redefine error, undefined func error\n\n### Step 7: Integration tests (integration_test.go)\n- Update eval()/evalErr() helpers to use Evaluator struct\n- Add tests:\n - Define and call single-param function\n - Define and call multi-param function\n - Cross-function calls\n - Nested function calls in expressions\n - Error: undefined function\n - Error: wrong argument count\n - Error: function redefinition\n - Error: undefined variable\n\n## Backward Compatibility\n- Parse() remains unchanged — returns ast.Node\n- Package-level Eval() remains — wraps New().Eval(node, nil)\n- Existing tests must continue to pass at every step\n"
CALLING TOOL: file_read {"path":"README.md"} $$$ "# matheval\n\nA math expression evaluator with an interactive REPL, written in Go.\n\n## Features\n\n- Arithmetic operators: +, -, *, /\n- Parentheses for grouping\n- Floating point numbers (including .5 syntax)\n- Correct operator precedence (* and / bind tighter than + and -)\n- Left-to-right associativity\n- Clear error messages with position reporting\n\n## Build\n\nsh\ngo build -o matheval ./cmd/matheval\n\n\n## Usage\n\nRun the REPL:\n\nsh\n./matheval\n\n\nThen type expressions:\n\n\n\u003e\u003e 2 + 3 * 4\n14\n\u003e\u003e (2 + 3) * 4\n20\n\u003e\u003e 7 / 2\n3.5\n\u003e\u003e 1 / 0\nerror: division by zero\n\n\nPress Ctrl+D (EOF) to exit.\n\nYou can also pipe input:\n\nsh\necho \"2 + 3\" | ./matheval\n\n\n## Architecture\n\n\nInput string → Lexer → Parser → AST → Evaluator → Result\n\n\n| Package | Responsibility |\n|-------------|---------------------------------------|\n| token | Token types and data structures |\n| lexer | Tokenizes input string |\n| ast | AST node types (NumberLit, BinaryExpr) |\n| parser | Recursive-descent parser |\n| evaluator | Walks AST and computes result |\n| repl | Read-eval-print loop |\n\n## Grammar\n\n\nexpr → term (('+' | '-') term)*\nterm → factor (('*' | '/') factor)*\nfactor → NUMBER | '(' expr ')'\n\n\n## Tests\n\nsh\ngo test ./...\n\n\nThis runs unit tests for each package plus integration tests covering the full pipeline.\n"
--- STOP_REASON: tool_use AI: Now I have full context. The README is outdated — it doesn't reflect the function definition feature described in docs/design.md and docs/plan_02.md. Let me update it. CALLING TOOL: file_write {"path":"README.md","contents":"# matheval\n\nA math expression evaluator with user-defined functions and an interactive REPL, written in Go.\n\n## Features\n\n- Arithmetic operators: +, -, *, /\n- Parentheses for grouping\n- Floating point numbers (including .5 syntax)\n- Correct operator precedence (* and / bind tighter than + and -)\n- Left-to-right associativity\n- User-defined functions with f(x) = x + 1 syntax\n- Multi-parameter functions: f(x, y) = x + y\n- Functions can call other user-defined functions (late binding)\n- Clear error messages with position reporting\n\n## Build\n\nsh\ngo build -o matheval ./cmd/matheval\n\n\n## Usage\n\nRun the REPL:\n\nsh\n./matheval\n\n\nThen type expressions and define functions:\n\n\n>> 2 + 3 * 4\n14\n>> (2 + 3) * 4\n20\n>> 7 / 2\n3.5\n>> 1 / 0\nerror: division by zero\n>> square(x) = x * x\ndefined square\n>> square(5)\n25\n>> add(x, y) = x + y\ndefined add\n>> add(2, 3)\n5\n>> hyp(a, b) = square(a) + square(b)\ndefined hyp\n>> hyp(3, 4)\n25\n\n\nPress Ctrl+D (EOF) to exit.\n\nYou can also pipe input:\n\nsh\necho \"2 + 3\" | ./matheval\n\n\n## Architecture\n\n\nInput string → Lexer → Parser → AST → Evaluator → Result\n\n\n| Package | Responsibility |\n|-------------|---------------------------------------------------------|\n| token | Token types and data structures |\n| lexer | Tokenizes input string |\n| ast | AST node types (NumberLit, BinaryExpr, Ident, FuncCall, FuncDef) |\n| parser | Recursive-descent parser (expressions and function definitions) |\n| evaluator | Stateful evaluator with function registry |\n| repl | Read-eval-print loop with persistent state |\n\n## Grammar\n\n\nline → funcdef | expr\nfuncdef → IDENT '(' params ')' '=' expr\nparams → IDENT (',' IDENT)*\nexpr → term (('+' | '-') term)*\nterm → factor (('*' | '/') factor)*\nfactor → NUMBER | IDENT '(' args ')' | IDENT | '(' expr ')'\nargs → expr (',' expr)*\n\n\n## Function Rules\n\n- Define: name(params) = body — body is any expression using the parameters\n- Call: name(args) — arguments are arbitrary expressions\n- Redefinition: Not allowed (returns an error)\n- Cross-calling: Functions can call other user-defined functions\n- Late binding: References resolved at call time, not definition time\n\n## Tests\n\nsh\ngo test ./...\n\n\nThis runs unit tests for each package plus integration tests covering the full pipeline.\n"} $$$ "done"
--- STOP_REASON: tool_use CALLING TOOL: todo_item_mark_done {"id":"1","summary":"Updated README.md to reflect the full feature set documented in docs/design.md and docs/plan_02.md. Added: user-defined functions section, multi-parameter functions, cross-function calls, late binding, updated architecture table with new AST node types, extended grammar, function rules section, and REPL examples demonstrating function definitions and calls."} $$$ "done"
--- STOP_REASON: end_turn AI: Done. The README.md has been updated to reflect the full project as documented in the docs/ files. Key changes:
square(x) = x * x, add(x, y) = x + y, and cross-calling with hyp(a, b).Ident, FuncCall, FuncDef) and stateful evaluator.funcdef, params, args, IDENT, and FuncCall productions.interrupt: 2 ~/dev/src/math $