From 9d626124e12a6172faa0f3c70ee61350268489e9 Mon Sep 17 00:00:00 2001
From: Jacob Austin <ja3067@columbia.edu>
Date: Sat, 18 Apr 2020 18:47:53 -0400
Subject: [PATCH] added initial support for AddNode and MultNodes

---
 include/autoppl/expression/operator.hpp | 96 +++++++++++++++++++++++++
 test/CMakeLists.txt                     |  1 +
 test/expression/operator_unittest.cpp   | 31 ++++++++
 3 files changed, 128 insertions(+)
 create mode 100644 include/autoppl/expression/operator.hpp
 create mode 100644 test/expression/operator_unittest.cpp

diff --git a/include/autoppl/expression/operator.hpp b/include/autoppl/expression/operator.hpp
new file mode 100644
index 00000000..f50dbd94
--- /dev/null
+++ b/include/autoppl/expression/operator.hpp
@@ -0,0 +1,96 @@
+#pragma once
+
+
+#include <autoppl/expression/variable.hpp>
+
+namespace ppl {
+
+/*
+ * Node resulting from adding two Variables together, or a variable
+ * and an element of type Variable::value_t. Can be casted to value_t
+ * and returns the sum of the left and right subtrees.
+*/
+template <typename LeftChildType, typename RightChildType, typename ValueType>
+struct AddNode
+{
+    using value_t = ValueType;
+    AddNode(LeftChildType left, RightChildType right) : left_(left), right_(right) {
+        static_assert(std::is_convertible_v<LeftChildType, value_t>);
+        static_assert(std::is_convertible_v<RightChildType, value_t>);
+    }
+
+    operator value_t () const { return left_value() + right_value(); }
+
+    value_t left_value() const { return static_cast<value_t>(left_); }
+    value_t right_value() const { return static_cast<value_t>(right_); }
+
+private:
+    LeftChildType left_;
+    RightChildType right_;
+};
+
+//////////////////////////////////
+// Operator overloads for AddNode
+///////////////////////////////////
+
+template <typename ValueType>
+AddNode<ValueType, Variable<ValueType>, ValueType> operator+(ValueType left, Variable<ValueType> right) {
+    return AddNode<ValueType, Variable<ValueType>, ValueType>(left, right);
+}
+
+template <typename ValueType>
+AddNode<Variable<ValueType>, ValueType, ValueType> operator+(Variable<ValueType> left, ValueType right) {
+    return AddNode<Variable<ValueType>, ValueType, ValueType>(left, right);
+}
+
+template <typename ValueType>
+AddNode<Variable<ValueType>, Variable<ValueType>, ValueType> operator+(Variable<ValueType> left, Variable<ValueType> right) {
+    return AddNode<Variable<ValueType>, Variable<ValueType>, ValueType>(left, right);
+}
+
+
+/*
+ * Node resulting from multiplying two Variables together, or a variable
+ * and an element of type Variable::value_t. Can be casted to value_t
+ * and returns the product of the left and right subtrees.
+*/
+template <typename LeftChildType, typename RightChildType, typename ValueType>
+struct MultNode
+{
+    using value_t = ValueType;
+    MultNode(LeftChildType left, RightChildType right) : left_(left), right_(right) {
+        static_assert(std::is_convertible_v<LeftChildType, value_t>);
+        static_assert(std::is_convertible_v<RightChildType, value_t>);
+    }
+
+    operator value_t () const { return left_value() * right_value(); }
+
+    value_t left_value() const { return static_cast<value_t>(left_); }
+    value_t right_value() const { return static_cast<value_t>(right_); }
+
+private:
+    LeftChildType left_;
+    RightChildType right_;
+};
+
+//////////////////////////////////
+// Operator overloads for MultNode
+///////////////////////////////////
+
+template <typename ValueType>
+MultNode<ValueType, Variable<ValueType>, ValueType> operator*(ValueType left, Variable<ValueType> right) {
+    return MultNode<ValueType, Variable<ValueType>, ValueType>(left, right);
+}
+
+template <typename ValueType>
+MultNode<Variable<ValueType>, ValueType, ValueType> operator*(Variable<ValueType> left, ValueType right) {
+    return MultNode<Variable<ValueType>, ValueType, ValueType>(left, right);
+}
+
+template <typename ValueType>
+MultNode<Variable<ValueType>, Variable<ValueType>, ValueType> operator*(Variable<ValueType> left, Variable<ValueType> right) {
+    return MultNode<Variable<ValueType>, Variable<ValueType>, ValueType>(left, right);
+}
+
+
+} // ppl
\ No newline at end of file
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 670e3d9a..95071834 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -11,6 +11,7 @@ endif()
 
 add_executable(expression_unittest
     ${CMAKE_CURRENT_SOURCE_DIR}/expression/model_unittest.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/expression/operator_unittest.cpp
     )
 target_compile_options(expression_unittest PRIVATE -g -Wall -Werror -Wextra)
 target_include_directories(expression_unittest PRIVATE ${GTEST_DIR}/include)
diff --git a/test/expression/operator_unittest.cpp b/test/expression/operator_unittest.cpp
new file mode 100644
index 00000000..65619f6f
--- /dev/null
+++ b/test/expression/operator_unittest.cpp
@@ -0,0 +1,31 @@
+#include <cmath>
+#include <array>
+#include "gtest/gtest.h"
+#include <autoppl/expression/variable.hpp>
+#include <autoppl/expression/operator.hpp>
+
+namespace ppl {
+
+//////////////////////////////////////////////////////
+// Model with one RV TESTS
+//////////////////////////////////////////////////////
+
+/*
+ * Fixture for testing one var with distribution.
+ */
+struct add_node_fixture : ::testing::Test
+{
+protected:
+    Variable<double> x {3.0};
+    Variable<double> y {4.0};
+};
+
+TEST_F(add_node_fixture, add_node_test) {
+    AddNode<Variable<double>, Variable<double>, double> addnode = x + y;
+    EXPECT_EQ(static_cast<double>(addnode), 7.0);
+
+    MultNode<Variable<double>, Variable<double>, double> multnode = x * y;
+    EXPECT_EQ(static_cast<double>(multnode), 12.0);
+}
+
+} // ppl
\ No newline at end of file