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

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

@@ -0,0 +1,149 @@
+"""
+Recursive-descent parser for the calc expression grammar.
+
+Grammar:
+    expr    = term   ( ('+' | '-') term   )*
+    term    = unary  ( ('*' | '/') unary  )*
+    unary   = '-' unary | primary
+    primary = NUMBER | '(' expr ')'
+
+AST node shapes (stable contract for the evaluator):
+    Num(value)             — numeric literal; .value is int or float
+    BinOp(op, left, right) — binary operation; .op is '+', '-', '*', or '/'
+    Unary(op, operand)     — unary prefix; .op is '-'
+"""
+
+
+class ParseError(Exception):
+    pass
+
+
+# ---------------------------------------------------------------------------
+# AST nodes
+# ---------------------------------------------------------------------------
+
+class Num:
+    __slots__ = ('value',)
+
+    def __init__(self, value):
+        self.value = value
+
+    def __repr__(self):
+        return f'Num({self.value!r})'
+
+    def __eq__(self, other):
+        return isinstance(other, Num) and self.value == other.value
+
+
+class BinOp:
+    __slots__ = ('op', 'left', 'right')
+
+    def __init__(self, op: str, left, right):
+        self.op = op
+        self.left = left
+        self.right = right
+
+    def __repr__(self):
+        return f'BinOp({self.op!r}, {self.left!r}, {self.right!r})'
+
+    def __eq__(self, other):
+        return (isinstance(other, BinOp)
+                and self.op == other.op
+                and self.left == other.left
+                and self.right == other.right)
+
+
+class Unary:
+    __slots__ = ('op', 'operand')
+
+    def __init__(self, op: str, operand):
+        self.op = op
+        self.operand = operand
+
+    def __repr__(self):
+        return f'Unary({self.op!r}, {self.operand!r})'
+
+    def __eq__(self, other):
+        return (isinstance(other, Unary)
+                and self.op == other.op
+                and self.operand == other.operand)
+
+
+# ---------------------------------------------------------------------------
+# Parser
+# ---------------------------------------------------------------------------
+
+class _Parser:
+    def __init__(self, tokens):
+        self._tokens = tokens
+        self._pos = 0
+
+    def _peek(self):
+        return self._tokens[self._pos]
+
+    def _advance(self):
+        tok = self._tokens[self._pos]
+        self._pos += 1
+        return tok
+
+    def _expect(self, kind):
+        tok = self._peek()
+        if tok.kind != kind:
+            raise ParseError(
+                f"Expected {kind}, got {tok.kind!r} ({tok.value!r})"
+            )
+        return self._advance()
+
+    # expr = term ( ('+' | '-') term )*
+    def _expr(self):
+        node = self._term()
+        while self._peek().kind in ('PLUS', 'MINUS'):
+            op = self._advance().value
+            node = BinOp(op, node, self._term())
+        return node
+
+    # term = unary ( ('*' | '/') unary )*
+    def _term(self):
+        node = self._unary()
+        while self._peek().kind in ('STAR', 'SLASH'):
+            op = self._advance().value
+            node = BinOp(op, node, self._unary())
+        return node
+
+    # unary = '-' unary | primary
+    def _unary(self):
+        if self._peek().kind == 'MINUS':
+            self._advance()
+            return Unary('-', self._unary())
+        return self._primary()
+
+    # primary = NUMBER | '(' expr ')'
+    def _primary(self):
+        tok = self._peek()
+        if tok.kind == 'NUMBER':
+            self._advance()
+            return Num(tok.value)
+        if tok.kind == 'LPAREN':
+            self._advance()
+            node = self._expr()
+            self._expect('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(self):
+        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 after expression: {tok.kind!r} ({tok.value!r})"
+            )
+        return node
+
+
+def parse(tokens) -> object:
+    """Parse a token list produced by `calc.lexer.tokenize` into an AST."""
+    return _Parser(tokens).parse()