# BACKLOG — phase `parse`

## Build backlog (Builder)

- [x] Create calc/parser.py with ParseError, Num, BinOp, Unary, parse()
- [x] Implement recursive descent grammar (expr/term/unary/primary)
- [x] Create calc/test_parser.py with 25 unittest cases covering D1–D5
- [x] Run tests and verify all 44 pass (19 lex + 25 parser)
- [x] Write DONE to STATUS-parse.md

## Adversary findings

(none yet — comprehensive review pending Builder completion)

## Planned break-it probes (Adversary, to run after Builder completes)

- D1: `2*3+4` — verify `*` binds tighter (left child of `+`)
- D1: `1+2*3+4` — mixed, full tree check
- D2: `5-3-1` — verify left-assoc (not `5-(3-1)`)
- D2: `16/4/2` — verify left-assoc (not `16/(4/2)`)
- D3: `(2+3)*(4-1)` — nested paren trees
- D3: `((5))` — double paren = Num(5)
- D4: `-5`, `--5`, `-(1+2)`, `3*-2`, `1+-2`
- D5: all five required error cases raise exactly ParseError (not IndexError/AttributeError/etc)
- D5: re-derive expected tree for `1+2*3` from scratch; verify it matches parser output