From 7367903fd4470a1e1b0724ddccf4258218f3bb95 Mon Sep 17 00:00:00 2001
From: Ravenwater <theo@stillwater-sc.com>
Date: Tue, 10 Sep 2024 11:16:23 -0400
Subject: [PATCH] adding a playground skeleton for lazy evaluation experiments

---
 playground/CMakeLists.txt              |   1 +
 playground/float_to_decimal_string.cpp |   4 +-
 playground/lazy_evaluation.cpp         | 114 +++++++++++++++++++++++++
 3 files changed, 117 insertions(+), 2 deletions(-)
 create mode 100644 playground/lazy_evaluation.cpp

diff --git a/playground/CMakeLists.txt b/playground/CMakeLists.txt
index c69dd4f8c..ad1f526c1 100644
--- a/playground/CMakeLists.txt
+++ b/playground/CMakeLists.txt
@@ -9,6 +9,7 @@ set(REAL_SRCS efunc_posits.cpp
 	 skeleton.cpp 
 	 type_test.cpp
 	 float_to_decimal_string.cpp
+	 lazy_evaluation.cpp
 )
 
 compile_all("true" "playground" "Playground" "${REAL_SRCS}")
diff --git a/playground/float_to_decimal_string.cpp b/playground/float_to_decimal_string.cpp
index 0f9465f99..ad3d23ab0 100644
--- a/playground/float_to_decimal_string.cpp
+++ b/playground/float_to_decimal_string.cpp
@@ -15,7 +15,7 @@
 
 int main(int argc, char** argv)
 try {
-	using namespace sw::universal;
+    using namespace sw::universal;
 
     float f = 3.14156;
     float x = f * 1e6;
@@ -50,7 +50,7 @@ try {
 
     std::cout << "Custom conversion: " << S << std::endl;
 
-	return EXIT_SUCCESS;
+    return EXIT_SUCCESS;
 }
 catch (char const* msg) {
 	std::cerr << "Caught exception: " << msg << std::endl;
diff --git a/playground/lazy_evaluation.cpp b/playground/lazy_evaluation.cpp
new file mode 100644
index 000000000..a0c525a6f
--- /dev/null
+++ b/playground/lazy_evaluation.cpp
@@ -0,0 +1,114 @@
+// lazy_evaluation.cpp: experiments in lazy evaluation and state management
+//
+// Copyright (C) 2017 Stillwater Supercomputing, Inc.
+// SPDX-License-Identifier: MIT
+//
+// This file is part of the universal numbers project, which is released under an MIT Open Source license.
+#include <iostream>
+#include <type_traits>
+
+#include <universal/number/cfloat/cfloat.hpp>
+
+namespace test1 {
+    template<typename T>
+    struct Expression {
+        T value;
+
+        Expression(T v) : value(v) {}
+
+        template<typename U>
+        Expression<decltype(value + U::value)> operator+(const Expression<U>& other) const {
+            return Expression<decltype(value + U::value)>(value + other.value);
+        }
+
+        template<typename U>
+        Expression<decltype(value* U::value)> operator*(const Expression<U>& other) const {
+            return Expression<decltype(value * U::value)>(value * other.value);
+        }
+
+        operator T() const { return value; }
+
+    };
+}
+
+namespace test2 {
+
+    template <typename T>
+    class Expression {
+    private:
+        T value;
+
+    public:
+        Expression(T value) : value(value) {}
+
+        template <typename U>
+        auto operator+(const Expression<U>& other) const -> decltype(value + other.value) {
+            return Expression<decltype(value + other.value)>(value + other.value);
+        }
+
+        template <typename U>
+        auto operator*(const Expression<U>& other) const -> decltype(value * other.value) {
+            return Expression<decltype(value * other.value)>(value * other.value);
+        }
+
+        operator T() const { return T(value); }
+
+    };
+}
+
+int main(int argc, char** argv)
+try {
+    using namespace sw::universal;
+
+    // Expression as defined above only works on native types as some implicit conversions make the class definition simpler
+    // precondition is definition of operator+(), operator*(), and conversion operator
+
+
+    {  
+        using Real = float;
+        test1::Expression<Real> a(2.0), b(3.0), c(4.0);
+
+        test1::Expression<Real> result = a * (b + c);
+
+        std::cout << result << '\n';
+    }
+
+    {
+        using Real = cfloat<24,8, uint32_t, true, false, false>;
+
+        test2::Expression<Real> a(2.5), b(3.0), c(4.0);
+
+        // test2::Expression<Real> result = a * (b + c);
+        // required: binary operator that supports: Expression * cfloat
+
+        test2::Expression<Real> tmpSum = (b + c);
+
+        test2::Expression<Real> result = a * tmpSum;
+
+        Real value = Real(result);
+
+        std::cout << value << '\n';
+    }
+
+    return EXIT_SUCCESS;
+}
+catch (char const* msg) {
+	std::cerr << "Caught exception: " << msg << std::endl;
+	return EXIT_FAILURE;
+}
+catch (const sw::universal::universal_arithmetic_exception& err) {
+	std::cerr << "Uncaught universal arithmetic exception: " << err.what() << std::endl;
+	return EXIT_FAILURE;
+}
+catch (const sw::universal::universal_internal_exception& err) {
+	std::cerr << "Uncaught universal internal exception: " << err.what() << std::endl;
+	return EXIT_FAILURE;
+}
+catch (const std::runtime_error& err) {
+	std::cerr << "Uncaught runtime exception: " << err.what() << std::endl;
+	return EXIT_FAILURE;
+}
+catch (...) {
+	std::cerr << "Caught unknown exception" << std::endl;
+	return EXIT_FAILURE;
+}