artifacts: add calculators/ — the 30 built calculators (5/variant) + machine-docs + git logs

calculators/builder-adversary-min/run-05/calc/parser.py

@@ -0,0 +1,126 @@
+"""
+Recursive-descent parser for arithmetic expressions.
+
+AST node shapes:
+    Num(value)              — a numeric literal; value is int or float
+    BinOp(op, left, right)  — binary operation; op is '+', '-', '*', or '/'
+    Unary(op, operand)      — unary minus; op is '-'
+
+Grammar (precedence low → high):
+    expr    := term   (('+' | '-') term)*
+    term    := unary  (('*' | '/') unary)*
+    unary   := '-' unary | primary
+    primary := NUMBER | '(' expr ')'
+"""
+from __future__ import annotations
+from dataclasses import dataclass
+from typing import Union
+
+
+class ParseError(Exception):
+    pass
+
+
+@dataclass
+class Num:
+    value: Union[int, float]
+
+    def __repr__(self) -> str:
+        return f"Num({self.value!r})"
+
+
+@dataclass
+class BinOp:
+    op: str
+    left: "Node"
+    right: "Node"
+
+    def __repr__(self) -> str:
+        return f"BinOp({self.op!r}, {self.left!r}, {self.right!r})"
+
+
+@dataclass
+class Unary:
+    op: str
+    operand: "Node"
+
+    def __repr__(self) -> str:
+        return f"Unary({self.op!r}, {self.operand!r})"
+
+
+Node = Union[Num, BinOp, Unary]
+
+
+class _Parser:
+    def __init__(self, tokens: list) -> None:
+        self._tokens = tokens
+        self._pos = 0
+
+    def _peek(self):
+        return self._tokens[self._pos]
+
+    def _consume(self, kind: str = None):
+        tok = self._tokens[self._pos]
+        if kind is not None and tok.kind != kind:
+            raise ParseError(
+                f"expected {kind!r}, got {tok.kind!r} ({tok.value!r})"
+            )
+        self._pos += 1
+        return tok
+
+    def parse(self) -> Node:
+        if self._peek().kind == "EOF":
+            raise ParseError("empty input")
+        node = self._expr()
+        if self._peek().kind != "EOF":
+            tok = self._peek()
+            raise ParseError(
+                f"unexpected token {tok.kind!r} ({tok.value!r}) after expression"
+            )
+        return node
+
+    def _expr(self) -> Node:
+        node = self._term()
+        while self._peek().kind in ("PLUS", "MINUS"):
+            op = self._consume().value
+            right = self._term()
+            node = BinOp(op, node, right)
+        return node
+
+    def _term(self) -> Node:
+        node = self._unary()
+        while self._peek().kind in ("STAR", "SLASH"):
+            op = self._consume().value
+            right = self._unary()
+            node = BinOp(op, node, right)
+        return node
+
+    def _unary(self) -> Node:
+        if self._peek().kind == "MINUS":
+            op = self._consume().value
+            operand = self._unary()
+            return Unary(op, operand)
+        return self._primary()
+
+    def _primary(self) -> Node:
+        tok = self._peek()
+        if tok.kind == "NUMBER":
+            self._consume()
+            return Num(tok.value)
+        if tok.kind == "LPAREN":
+            self._consume()
+            node = self._expr()
+            if self._peek().kind != "RPAREN":
+                raise ParseError(
+                    f"expected ')' but got {self._peek().kind!r}"
+                )
+            self._consume("RPAREN")
+            return node
+        raise ParseError(
+            f"unexpected token {tok.kind!r} ({tok.value!r})"
+        )
+
+
+def parse(tokens: list) -> Node:
+    """Parse a token list (from lexer.tokenize) into an AST Node."""
+    return _Parser(tokens).parse()