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

calculators/builder-adversary/run-03/calc/parser.py

@@ -0,0 +1,123 @@
+"""Recursive-descent parser for arithmetic expressions.
+
+AST nodes:
+  Num(value)              — numeric literal
+  BinOp(op, left, right)  — binary op; op in {'+', '-', '*', '/'}
+  Unary(op, operand)      — unary op; op == '-'
+"""
+from dataclasses import dataclass
+from typing import Union
+from .lexer import Token
+
+
+class ParseError(Exception):
+    """Raised on malformed input."""
+
+
+@dataclass
+class Num:
+    value: Union[int, float]
+
+    def __repr__(self):
+        return f"Num({self.value!r})"
+
+
+@dataclass
+class BinOp:
+    op: str
+    left: object
+    right: object
+
+    def __repr__(self):
+        return f"BinOp({self.op!r}, {self.left!r}, {self.right!r})"
+
+
+@dataclass
+class Unary:
+    op: str
+    operand: object
+
+    def __repr__(self):
+        return f"Unary({self.op!r}, {self.operand!r})"
+
+
+_KIND_TO_OP = {
+    'PLUS': '+',
+    'MINUS': '-',
+    'STAR': '*',
+    'SLASH': '/',
+}
+
+
+class _Parser:
+    def __init__(self, tokens: list):
+        self._tokens = tokens
+        self._pos = 0
+
+    def _peek(self) -> Token:
+        return self._tokens[self._pos]
+
+    def _consume(self, kind: str = None) -> Token:
+        tok = self._tokens[self._pos]
+        if kind is not None and tok.kind != kind:
+            raise ParseError(f"expected {kind!r}, got {tok.kind!r}")
+        self._pos += 1
+        return tok
+
+    def parse(self):
+        if self._peek().kind == 'EOF':
+            raise ParseError("empty expression")
+        node = self._expr()
+        if self._peek().kind != 'EOF':
+            raise ParseError(f"unexpected token {self._peek().kind!r}")
+        return node
+
+    def _expr(self):
+        node = self._term()
+        while self._peek().kind in ('PLUS', 'MINUS'):
+            op = _KIND_TO_OP[self._consume().kind]
+            right = self._term()
+            node = BinOp(op, node, right)
+        return node
+
+    def _term(self):
+        node = self._unary()
+        while self._peek().kind in ('STAR', 'SLASH'):
+            op = _KIND_TO_OP[self._consume().kind]
+            right = self._unary()
+            node = BinOp(op, node, right)
+        return node
+
+    def _unary(self):
+        if self._peek().kind == 'MINUS':
+            self._consume()
+            return Unary('-', self._unary())
+        return self._primary()
+
+    def _primary(self):
+        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("unclosed parenthesis, expected ')'")
+            self._consume()
+            return node
+        if tok.kind == 'EOF':
+            raise ParseError("unexpected end of input")
+        raise ParseError(f"unexpected token {tok.kind!r}")
+
+
+def parse(tokens: list):
+    """Parse a token list into an AST.
+
+    Returns:
+        Num | BinOp | Unary — root node.
+
+    Raises:
+        ParseError: on any malformed input.
+    """
+    return _Parser(tokens).parse()