From 5de287a6e7ebf2e12f4f66371fb9b471fe99aa3a Mon Sep 17 00:00:00 2001
From: Ruofan XU <47302112+SleepyRoy@users.noreply.github.com>
Date: Fri, 15 Jan 2021 21:10:30 +0800
Subject: [PATCH] tests: add test of sumtype-based binary tree (#8121)

---
 vlib/v/tests/sum_type_test.v | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/vlib/v/tests/sum_type_test.v b/vlib/v/tests/sum_type_test.v
index c71ce7d61f..2778cc4496 100644
--- a/vlib/v/tests/sum_type_test.v
+++ b/vlib/v/tests/sum_type_test.v
@@ -539,3 +539,39 @@ fn handle(e Expr) string {
 	}
 	return ''
 }
+
+// for a binary tree
+struct Empty {}
+
+struct Node_ {
+	// TODO: make value generic once it's more robust 
+	value f64
+	left  Tree
+	right Tree
+}
+
+type Tree = Empty | Node_
+
+fn size(tree Tree) int {
+	return match tree {
+		// TODO: remove int() here once match gets smarter
+		Empty { int(0) }
+		Node_ { 1 + size(tree.left) + size(tree.right) }
+	}
+}
+
+fn sum(tree Tree) f64 {
+	return match tree {
+		// TODO: remove f64() here once match gets smarter
+		Empty { f64(0) }
+		Node_ { tree.value + sum(tree.left) + sum(tree.right) }
+	}
+}
+
+fn test_binary_tree_operation() {
+	left := Node_{0.2, Empty{}, Empty{}}
+	right := Node_{0.3, Empty{}, Node_{0.4, Empty{}, Empty{}}}
+	tree := Node_{0.5, left, right}
+	assert size(tree) == 4
+	assert sum(tree) == 1.4
+}