calculator: add printer visitor

calculator/calculator/print/__init__.py

@@ -0,0 +1 @@
+from .printer import Printer

calculator/calculator/print/printer.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+import dataclasses
+from typing import TYPE_CHECKING
+
+from calculator.ast.visit import Visitor
+from calculator.core.operations import (
+    identity,
+    int_div,
+    minus,
+    negate,
+    plus,
+    pow,
+    times,
+)
+from pydantic.dataclasses import dataclass
+
+if TYPE_CHECKING:
+    from calculator.ast import BinOp, Constant, Node, UnaryOp
+
+OP_TO_STR = {
+    plus: "+",
+    minus: "-",
+    times: "*",
+    int_div: "/",
+    pow: "^",
+    identity: "+",
+    negate: "-",
+}
+
+
+@dataclass
+class Printer(Visitor):
+    """
+    Print a Tree
+    """
+
+    indent: int = dataclasses.field(default=0, init=False)
+
+    def print(self, n: Node) -> None:
+        n.accept(self)
+
+    def visit_constant(self, c: Constant) -> None:
+        print(" " * self.indent + str(c.value))
+
+    def visit_binop(self, b: BinOp) -> None:
+        print(" " * self.indent + OP_TO_STR[b.op])
+        self.indent += 2
+        self.print(b.lhs)
+        self.print(b.rhs)
+        self.indent -= 2
+
+    def visit_unaryop(self, b: UnaryOp) -> None:
+        print(" " * self.indent + OP_TO_STR[b.op])
+        self.indent += 2
+        self.print(b.rhs)
+        self.indent -= 2

calculator/calculator/print/test_printer.py

@@ -0,0 +1,28 @@
+import pytest
+from calculator.parse import parse_infix
+
+from .printer import Printer
+
+
+def print_test_helper(input: str, expected: str, capsys):
+    Printer().print(parse_infix(input))
+    out, __ = capsys.readouterr()
+    assert out == expected
+
+
+def test_printer_constant(capsys):
+    print_test_helper("42", "42\n", capsys)
+
+
+def test_printer_negated_constant(capsys):
+    print_test_helper("-42", "-\n  42\n", capsys)
+
+
+def test_printer_binaryop(capsys):
+    print_test_helper("12 + 27", "+\n  12\n  27\n", capsys)
+
+
+def test_print_complex_expression(capsys):
+    print_test_helper(
+        "12 + 27 * 42 ^51", "+\n  12\n  *\n    27\n    ^\n      42\n      51\n", capsys
+    )