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

calculators/builder-adversary/run-04/calc/parser.py

@@ -0,0 +1,139 @@
+"""Recursive-descent parser for arithmetic expressions.
+
+Grammar (precedence low → high):
+    expr   ::= term  (('+' | '-') term)*
+    term   ::= unary (('*' | '/') unary)*
+    unary  ::= '-' unary | primary
+    primary::= NUMBER | '(' expr ')'
+
+AST node shapes:
+    Num(value)                 – leaf; value is int or float
+    BinOp(op, left, right)     – op is '+', '-', '*', or '/'
+    Unary(op, operand)         – op is '-'
+"""
+from __future__ import annotations
+from dataclasses import dataclass
+from typing import List, Union
+
+from calc.lexer import Token
+
+
+class ParseError(Exception):
+    pass
+
+
+# ---------------------------------------------------------------------------
+# 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) -> Token:
+        tok = self._peek()
+        if tok.kind != kind:
+            raise ParseError(
+                f"expected {kind!r} but got {tok.kind!r} (value={tok.value!r})"
+            )
+        self._pos += 1
+        return tok
+
+    def _advance(self) -> Token:
+        tok = self._tokens[self._pos]
+        self._pos += 1
+        return tok
+
+    # expr ::= term (('+' | '-') term)*
+    def _expr(self) -> Node:
+        node = self._term()
+        while self._peek().kind in ('PLUS', 'MINUS'):
+            op_tok = self._advance()
+            right = self._term()
+            node = BinOp(op_tok.value, node, right)
+        return node
+
+    # term ::= unary (('*' | '/') unary)*
+    def _term(self) -> Node:
+        node = self._unary()
+        while self._peek().kind in ('STAR', 'SLASH'):
+            op_tok = self._advance()
+            right = self._unary()
+            node = BinOp(op_tok.value, node, right)
+        return node
+
+    # unary ::= '-' unary | primary
+    def _unary(self) -> Node:
+        if self._peek().kind == 'MINUS':
+            op_tok = self._advance()
+            return Unary(op_tok.value, self._unary())
+        return self._primary()
+
+    # primary ::= NUMBER | '(' expr ')'
+    def _primary(self) -> Node:
+        tok = self._peek()
+        if tok.kind == 'NUMBER':
+            self._advance()
+            return Num(tok.value)
+        if tok.kind == 'LPAREN':
+            self._advance()
+            node = self._expr()
+            self._consume('RPAREN')
+            return node
+        if tok.kind == 'EOF':
+            raise ParseError("unexpected end of input")
+        raise ParseError(f"unexpected token {tok.kind!r} (value={tok.value!r})")
+
+    def parse(self) -> Node:
+        if self._peek().kind == 'EOF':
+            raise ParseError("empty expression")
+        node = self._expr()
+        if self._peek().kind != 'EOF':
+            tok = self._peek()
+            raise ParseError(
+                f"unexpected token after expression: {tok.kind!r} (value={tok.value!r})"
+            )
+        return node
+
+
+def parse(tokens: List[Token]) -> Node:
+    """Parse a token list produced by calc.lexer.tokenize into an AST."""
+    return _Parser(tokens).parse()