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

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

@@ -0,0 +1,127 @@
+"""Recursive-descent parser for calc expressions.
+
+Grammar:
+    expr    := term (('+' | '-') term)*
+    term    := factor (('*' | '/') factor)*
+    factor  := '-' factor | primary
+    primary := NUMBER | '(' expr ')'
+
+Node shapes:
+    Num(value)              — a numeric literal; value is int or float
+    BinOp(op, left, right)  — op is one of '+' '-' '*' '/'
+    Unary(op, operand)      — op is '-'
+"""
+
+
+class ParseError(Exception):
+    pass
+
+
+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, 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, 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)
+
+
+class _Parser:
+    def __init__(self, tokens):
+        self._tokens = tokens
+        self._pos = 0
+
+    def _peek(self):
+        return self._tokens[self._pos]
+
+    def _consume(self, kind=None):
+        tok = self._tokens[self._pos]
+        if kind and tok.kind != kind:
+            raise ParseError(f'expected {kind}, got {tok.kind!r}')
+        self._pos += 1
+        return tok
+
+    def parse(self):
+        if self._peek().kind == 'EOF':
+            raise ParseError('empty input')
+        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 = self._consume().value
+            right = self._term()
+            node = BinOp(op, node, right)
+        return node
+
+    def _term(self):
+        node = self._factor()
+        while self._peek().kind in ('STAR', 'SLASH'):
+            op = self._consume().value
+            right = self._factor()
+            node = BinOp(op, node, right)
+        return node
+
+    def _factor(self):
+        if self._peek().kind == 'MINUS':
+            self._consume()
+            operand = self._factor()
+            return Unary('-', operand)
+        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(f'unclosed parenthesis, got {self._peek().kind!r}')
+            self._consume()
+            return node
+        raise ParseError(f'unexpected token {tok.kind!r}')
+
+
+def parse(tokens):
+    """Parse a token list from tokenize() and return an AST node."""
+    return _Parser(tokens).parse()