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

calculators/builder-adversary/run-01/calc/parser.py

@@ -0,0 +1,143 @@
+"""Recursive-descent parser for arithmetic expressions.
+
+AST node types:
+  Num(value)              -- a numeric literal (int or float)
+  BinOp(op, left, right)  -- binary operation; op in ('+','-','*','/')
+  Unary(op, operand)      -- unary operation; op == '-'
+
+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
+
+from calc.lexer import Token, tokenize
+
+
+class ParseError(Exception):
+    """Raised on syntactically invalid input."""
+
+
+# ---------------------------------------------------------------------------
+# AST nodes
+# ---------------------------------------------------------------------------
+
+@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]
+
+
+# ---------------------------------------------------------------------------
+# Parser
+# ---------------------------------------------------------------------------
+
+class _Parser:
+    def __init__(self, tokens: list[Token]) -> None:
+        self._tokens = tokens
+        self._pos = 0
+
+    def _peek(self) -> Token:
+        return self._tokens[self._pos]
+
+    def _consume(self, kind: str | None = None) -> Token:
+        tok = self._tokens[self._pos]
+        if kind is not None and tok.kind != kind:
+            raise ParseError(
+                f"Expected {kind}, 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_tok = self._consume()
+            op = op_tok.value  # '+' or '-'
+            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_tok = self._consume()
+            op = op_tok.value  # '*' or '/'
+            right = self._unary()
+            node = BinOp(op, node, right)
+        return node
+
+    def _unary(self) -> Node:
+        if self._peek().kind == 'MINUS':
+            self._consume('MINUS')
+            operand = self._unary()
+            return Unary('-', operand)
+        return self._primary()
+
+    def _primary(self) -> Node:
+        tok = self._peek()
+        if tok.kind == 'NUMBER':
+            self._consume('NUMBER')
+            return Num(tok.value)
+        if tok.kind == 'LPAREN':
+            self._consume('LPAREN')
+            node = self._expr()
+            if self._peek().kind != 'RPAREN':
+                raise ParseError(
+                    f"Expected ')' but got {self._peek().kind!r}"
+                )
+            self._consume('RPAREN')
+            return node
+        if tok.kind == 'EOF':
+            raise ParseError("Unexpected end of input")
+        raise ParseError(
+            f"Unexpected token {tok.kind!r} ({tok.value!r})"
+        )
+
+
+def parse(tokens: list[Token]) -> Node:
+    """Parse *tokens* (from lexer.tokenize) into an AST Node.
+
+    Raises ParseError on malformed input.
+    """
+    return _Parser(tokens).parse()