Add optional implementation

1 files changed, 39 insertions, 0 deletions

diff --git a/butl/optional b/butl/optional
new file mode 100644
index 0000000..fc34b33
--- /dev/null
+++ b/butl/optional
@@ -0,0 +1,39 @@
+// file      : butl/optional -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUTL_OPTIONAL
+#define BUTL_OPTIONAL
+
+namespace butl
+{
+  // Simple optional class template while waiting for std::optional.
+  //
+  template <typename T>
+  class optional
+  {
+  public:
+    typedef T value_type;
+
+    optional (): null_ (true) {}
+    optional (const T& v): value_ (v), null_ (false) {}
+    optional& operator= (const T& v) {value_ = v; null_ = false; return *this;}
+
+    T&       value () {return value_;}
+    const T& value () const {return value_;}
+
+    T*       operator-> () {return &value_;}
+    const T* operator-> () const {return &value_;}
+
+    T&       operator* () {return value_;}
+    const T& operator* () const {return value_;}
+
+    explicit operator bool () const {return !null_;}
+
+  private:
+    T value_;
+    bool null_;
+  };
+}
+
+#endif // BUTL_OPTIONAL