From f99d5a8356b4762b13397a5a796626d0ddb71566 Mon Sep 17 00:00:00 2001
From: Kyle Isom <kyle@imap.cc>
Date: Thu, 9 Nov 2023 00:38:01 -0800
Subject: [PATCH] Add integer square root to SCMP.

---
 CMakeLists.txt      |  2 +-
 include/scmp/Math.h |  7 +++++++
 src/scmp/Math.cc    | 32 ++++++++++++++++++++++++++++++++
 test/math.cc        | 30 ++++++++++++++++++++++++++++++
 4 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 427d0a0..a1b973d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.22)
 project(scsl LANGUAGES CXX
-        VERSION 1.1.3
+        VERSION 1.1.4
         DESCRIPTION "Shimmering Clarity Standard Library")
 
 set(CMAKE_CXX_STANDARD 14)
diff --git a/include/scmp/Math.h b/include/scmp/Math.h
index 72f9cba..34f2115 100644
--- a/include/scmp/Math.h
+++ b/include/scmp/Math.h
@@ -115,6 +115,13 @@ WithinTolerance(T a, T b, T epsilon)
 }
 
 
+/// \brief Integer square-root.
+///
+/// \param n A max-value integer whose square root should be returned.
+/// \return The square root of $n$.
+size_t	ISqrt(size_t n);
+
+
 } // namespace scmp
 
 
diff --git a/src/scmp/Math.cc b/src/scmp/Math.cc
index 738cf16..15318b6 100644
--- a/src/scmp/Math.cc
+++ b/src/scmp/Math.cc
@@ -151,5 +151,37 @@ DefaultEpsilon(int& epsilon)
 }
 
 
+size_t
+ISqrt(size_t n)
+{
+	if (n < 2) {
+		return n;
+	}
+
+	size_t	start = 0;
+	size_t	end = n / 2;
+	size_t	result = 0;
+
+	while (start <= end) {
+		auto middle = (start + end) >> 1;
+		result = middle * middle;
+		if (result == n) {
+			return middle;
+		}
+
+		if (result < n) {
+			start = middle + 1;
+			result = middle;
+		} else {
+			end = middle - 1;
+			result = middle;
+		}
+	}
+
+	return result;
+}
+
+
+
 } // namespace scmp
 
diff --git a/test/math.cc b/test/math.cc
index 44710e2..70df65b 100644
--- a/test/math.cc
+++ b/test/math.cc
@@ -116,6 +116,35 @@ RotateRadians()
 }
 
 
+bool
+IntegerSquareRoot()
+{
+	static std::vector<size_t> ns{
+	    // standard integer roots
+	    4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144,
+
+	    // a few float cases
+	    42, 90, 92
+	};
+	static std::vector<size_t> expected{
+	    // standard integer roots
+	    2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
+
+	    // a few float cases
+	    6, 9, 10
+	};
+
+	SCTEST_CHECK_EQ(ns.size(), expected.size());
+
+	for (size_t i = 0; i < ns.size(); i++) {
+		auto root = scmp::ISqrt(ns.at(i));
+		SCTEST_CHECK_EQ(root, expected.at(i));
+	}
+
+	return true;
+}
+
+
 } // anonymous namespace
 
 
@@ -148,6 +177,7 @@ main(int argc, char *argv[])
 	suite.AddTest("WithinToleranceFloat", WithinToleranceFloat);
 	suite.AddTest("WithinToleranceDouble", WithinToleranceDouble);
 	suite.AddTest("RotateRadians", RotateRadians);
+	suite.AddTest("IntegerSquareRoot", IntegerSquareRoot);
 
 	delete flags;
 	auto result = suite.Run();