[et] first draft

examples/et/1_first_draft.cpp

@@ -0,0 +1,48 @@
+#include <cstdio>
+
+struct Add {
+	template<typename T>
+	static auto eval(T lhs, T rhs) {
+		return lhs + rhs;
+	}
+};
+
+struct Mul {
+	template<typename T>
+	static auto eval(T lhs, T rhs) {
+		return lhs * rhs;
+	}
+};
+
+template<typename T>
+class Value {
+	T _value;
+
+public:
+	Value(T value): _value(value) {}
+
+	auto eval() const { return _value; }
+};
+
+template<typename Op, typename LHS, typename RHS>
+struct BinExpr {
+	LHS lhs;
+	RHS rhs;
+
+	auto eval() const {
+		return Op::eval(lhs.eval(), rhs.eval());
+	}
+};
+
+int main() {
+	using SubExpr = BinExpr<Mul, Value<int>, Value<int>>;
+	using MyExpr  = BinExpr<Add, Value<int>, SubExpr>;
+
+	int volatile v0 = 3, v1 = 5, v2 = 7;
+	int result;
+
+	MyExpr expr{{v0}, {{v1}, {v2}}};
+	result = expr.eval();
+
+	std::printf("%d\n", result);
+}