From 2ce052e54d55e9029eff00f0985e399fa1eb2c1a Mon Sep 17 00:00:00 2001
From: a1xd <68629610+a1xd@users.noreply.github.com>
Date: Wed, 29 Jul 2020 17:36:33 -0400
Subject: add sum types

---
 common/external/nillable.h | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 common/external/nillable.h

(limited to 'common/external/nillable.h')

diff --git a/common/external/nillable.h b/common/external/nillable.h
new file mode 100644
index 0000000..40cf01c
--- /dev/null
+++ b/common/external/nillable.h
@@ -0,0 +1,30 @@
+inline constexpr struct nil_t {} nil;
+
+// Requirements: T is default-constructible and trivially-destructible
+template<typename T>
+struct nillable {
+    bool has_value = false;
+    T value;
+
+    nillable() = default;
+
+    nillable(nil_t) : nillable() {}
+    nillable(const T& v) : has_value(true), value(v) {}
+
+    nillable& operator=(nil_t) {
+        has_value = false;
+        return *this;
+    }
+    nillable& operator=(const T& v) {
+        value = v;
+        has_value = true;
+        return *this;
+    }
+
+    const T* operator->() const { return &value; }
+    T* operator->() { return &value; }
+
+    explicit operator bool() const { return has_value; }
+};
+
+template<typename T> nillable(T)->nillable<T>;
-- 
cgit v1.2.3