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

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

@@ -0,0 +1,140 @@
+from dataclasses import dataclass
+from typing import Union
+from calc.lexer import Token
+
+
+class ParseError(Exception):
+    pass
+
+
+@dataclass
+class Num:
+    """Leaf node: a numeric literal."""
+    value: Union[int, float]
+
+    def __repr__(self):
+        return f"Num({self.value!r})"
+
+
+@dataclass
+class Unary:
+    """Unary operator node: op is '-', operand is the inner Node."""
+    op: str
+    operand: object
+
+    def __repr__(self):
+        return f"Unary({self.op!r}, {self.operand!r})"
+
+
+@dataclass
+class BinOp:
+    """Binary operator node. op is one of '+', '-', '*', '/'.
+    Precedence and associativity are encoded in the tree structure, not here.
+    """
+    op: str
+    left: object
+    right: object
+
+    def __repr__(self):
+        return f"BinOp({self.op!r}, {self.left!r}, {self.right!r})"
+
+
+Node = Union[Num, Unary, BinOp]
+
+
+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) -> Token:
+        tok = self._peek()
+        if tok.kind != kind:
+            raise ParseError(
+                f"expected {kind}, got {tok.kind!r} ({tok.value!r})"
+            )
+        self._pos += 1
+        return tok
+
+    def _advance(self) -> Token:
+        tok = self._tokens[self._pos]
+        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
+
+    # Grammar (lowest to highest precedence):
+    #   expr   -> term  (('+' | '-') term)*
+    #   term   -> unary (('*' | '/') unary)*
+    #   unary  -> '-' unary | primary
+    #   primary-> NUMBER | '(' expr ')'
+
+    def _expr(self) -> Node:
+        node = self._term()
+        while self._peek().kind in ('PLUS', 'MINUS'):
+            op_tok = self._advance()
+            op = op_tok.value
+            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._advance()
+            op = op_tok.value
+            right = self._unary()
+            node = BinOp(op, node, right)
+        return node
+
+    def _unary(self) -> Node:
+        if self._peek().kind == 'MINUS':
+            self._advance()
+            operand = self._unary()
+            return Unary('-', operand)
+        return self._primary()
+
+    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()
+            if self._peek().kind != 'RPAREN':
+                raise ParseError(
+                    f"expected ')' but got {self._peek().kind!r}"
+                )
+            self._advance()
+            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) -> Node:
+    """Parse a token list (from lexer.tokenize) into an AST Node.
+
+    AST node shapes:
+      Num(value)              — numeric literal
+      Unary('-', operand)     — unary negation
+      BinOp(op, left, right)  — binary operation; op in {'+','-','*','/'}
+
+    Raises ParseError on malformed input.
+    """
+    return _Parser(tokens).parse()