# STATUS-parse

Phase: `parse`
Files: `calc/parser.py`, `calc/test_parser.py`

## AST Shape

```
Num(value)              — leaf; value is int or float
BinOp(op, left, right)  — op ∈ {'+', '-', '*', '/'}; left and right are Nodes
Unary(op, operand)      — op is '-'; operand is a Node
```

All nodes are `@dataclass` with custom `__repr__`.  
`parse(tokens) -> Node` accepts the list returned by `calc.lexer.tokenize`.  
`ParseError(Exception)` is raised for all malformed input.

## Gate Verification

### D1 — Precedence
**Command:** `python -c "from calc.lexer import tokenize; from calc.parser import parse; print(parse(tokenize('1+2*3')))"`  
**Expected:** `BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))`  
**Observed:** `BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))` ✓ **PASS**

### D2 — Left Associativity
**Command:** parse `8-3-2` and `8/4/2`  
**Expected:** `BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))` and `BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))`  
**Observed:** Both matched exactly ✓ **PASS**

### D3 — Parentheses
**Command:** parse `(1+2)*3`  
**Expected:** `BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))`  
**Observed:** `BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))` ✓ **PASS**

### D4 — Unary Minus
**Commands:** parse `-5`, `-(1+2)`, `3 * -2`  
**Expected:** `Unary('-', Num(5))`, `Unary('-', BinOp('+', Num(1), Num(2)))`, `BinOp('*', Num(3), Unary('-', Num(2)))`  
**Observed:** All three matched exactly ✓ **PASS**

### D5 — Errors
**Inputs tested:** `"1 +"`, `"(1"`, `"1 2"`, `")("`, `""`  
**Expected:** Each raises `ParseError`  
**Observed:**
- `"1 +"` → `ParseError: unexpected end of input` ✓
- `"(1"` → `ParseError: unclosed '(' — expected ')'` ✓
- `"1 2"` → `ParseError: unexpected token Token(kind='NUMBER', value=2) after expression` ✓
- `")("` → `ParseError: unexpected token 'RPAREN' (')')` ✓
- `""` → `ParseError: unexpected end of input` ✓
**PASS**

### D6 — Tests Green
**Command:** `python -m unittest -q`  
**Expected:** 0 failures  
**Observed:** `Ran 35 tests in 0.001s — OK` ✓ **PASS**

## DONE