Match, match_case, and MatchValue

src/latexify/codegen/function_codegen.py

@@ -652,6 +652,67 @@ def visit_IfExp(self, node: ast.IfExp) -> str:
         latex += self.visit(current_expr)
         return latex + r", & \mathrm{otherwise} \end{array} \right."
 
+    def visit_Match(self, node: ast.Match) -> str:
+        """Visit a match node"""
+        latex = r"\left\{ \begin{array}{ll} "
+        subject_latex = self.visit(node.subject)        
+        for match_case in node.cases:
+            if len(match_case.body) != 1:
+                raise exceptions.LatexifySyntaxError(
+                    "Multiple statements are not supported in Match nodes."
+                )
+            true_latex = self.visit(match_case.body[0])
+            cond_latex = self.visit(match_case.pattern)
+            latex += true_latex + r", & \mathrm{if} \ " + subject_latex + cond_latex + r" \\ "
+
+        latex += r"\end{array} \right."
+        return latex
+
+    def visit_MatchValue(self, node: ast.MatchValue) -> str:
+        """Visit a MatchValue node"""
+        latex = self.visit(node.value)
+        return " = " + latex
+
+    def _reduce_stop_parameter(self, node: ast.BinOp) -> str:
+        # ast.Constant class is added in Python 3.8
+        # ast.Num is the relevant node type in previous versions
+        if sys.version_info.minor < 8:
+            if isinstance(node.right, ast.Num):
+                if isinstance(node.op, ast.Add):
+                    if node.right.n == 1:
+                        upper = "{" + self.visit(node.left) + "}"
+                    else:
+                        reduced_constant = ast.Num(node.right.n - 1)
+                        new_node = ast.BinOp(node.left, node.op, reduced_constant)
+                        upper = "{" + self.visit(new_node) + "}"
+                else:
+                    if node.right.n == -1:
+                        upper = "{" + self.visit(node.left) + "}"
+                    else:
+                        reduced_constant = ast.Num(node.right.n + 1)
+                        new_node = ast.BinOp(node.left, node.op, reduced_constant)
+                        upper = "{" + self.visit(new_node) + "}"
+            else:
+                upper = "{" + self.visit(node) + "}"
+        else:
+            if isinstance(node.right, ast.Constant):
+                if isinstance(node.op, ast.Add):
+                    if node.right.value == 1:
+                        upper = "{" + self.visit(node.left) + "}"
+                    else:
+                        reduced_constant = ast.Constant(node.right.value - 1)
+                        new_node = ast.BinOp(node.left, node.op, reduced_constant)
+                        upper = "{" + self.visit(new_node) + "}"
+                else:
+                    if node.right.value == -1:
+                        upper = "{" + self.visit(node.left) + "}"
+                    else:
+                        reduced_constant = ast.Constant(node.right.value + 1)
+                        new_node = ast.BinOp(node.left, node.op, reduced_constant)
+                        upper = "{" + self.visit(new_node) + "}"
+            else:
+                upper = "{" + self.visit(node) + "}"
+
     def _reduce_stop_parameter(self, node: ast.expr) -> ast.expr:
         """Adjusts the stop expression of the range.
 

src/latexify/codegen/function_codegen_test.py

@@ -10,7 +10,6 @@
 from latexify import ast_utils, exceptions, test_utils
 from latexify.codegen import FunctionCodegen, function_codegen
 
-
 def test_generic_visit() -> None:
     class UnknownNode(ast.AST):
         pass
@@ -915,6 +914,56 @@ def test_use_set_symbols_compare(code: str, latex: str) -> None:
     assert function_codegen.FunctionCodegen(use_set_symbols=True).visit(tree) == latex
 
 
+def test_matchvalue() -> None:
+    tree = ast.parse(
+        textwrap.dedent(
+        """
+        match x:
+            case 0:
+                return 1
+        """
+        )
+    ).body[0]
+
+    assert FunctionCodegen().visit(tree) == r"\left\{ \begin{array}{ll} {1}, & \mathrm{if} \ x = {0} \\ \end{array} \right."
+
+
+def test_multiple_matchvalue() -> None:
+    tree = ast.parse(
+        textwrap.dedent(
+        """
+        match x:
+            case 0:
+                return 1
+            case 1:
+                return 2
+        """
+        )
+    ).body[0]
+
+    assert FunctionCodegen().visit(tree) == r"\left\{ \begin{array}{ll} {1}, & \mathrm{if} \ x = {0} \\ {2}, & \mathrm{if} \ x = {1} \\ \end{array} \right."
+
+def test_matchvalue_mutliple_statements() -> None:
+    tree = ast.parse(
+        textwrap.dedent(
+        """
+        match x:
+            case 0:
+                x = 5
+                return 1
+            case 1:
+                return 2
+        """
+        )
+    ).body[0]
+
+    with pytest.raises(
+        exceptions.LatexifySyntaxError,
+        match=r"Multiple statements are not supported in Match nodes.",
+    ):
+        FunctionCodegen().visit(tree)
+
+
 @pytest.mark.parametrize(
     "code,latex",
     [
@@ -959,3 +1008,4 @@ def test_numpy_array(code: str, latex: str) -> None:
     tree = ast_utils.parse_expr(code)
     assert isinstance(tree, ast.Call)
     assert function_codegen.FunctionCodegen().visit(tree) == latex
+