gcc/d/dmd/root/optional.h

   1 #pragma once
   2
   3 /**
   4  * Optional implementation.
   5  *
   6  * Copyright:   Copyright (C) 1999-2021 by The D Language Foundation, All Rights Reserved
   7  * Authors:     $(LINK2 http://www.digitalmars.com, Walter Bright)
   8  * License:     $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
   9  * Source:      $(LINK2 https://github.com/dlang/dmd/blob/master/src/dmd/root/optional.h, root/_optional.h)
  10  * Documentation:  https://dlang.org/phobos/dmd_root_optional.html
  11  * Coverage:    https://codecov.io/gh/dlang/dmd/src/master/src/dmd/root/optional.h
  12  */
  13
  14 /// Optional type that is either `empty` or contains a value of type `T`
  15 template<typename T>
  16 struct Optional final
  17 {
  18 private:
  19     /** the value (if present) **/
  20     T value;
  21
  22     /** whether `value` is set **/
  23     bool present;
  24
  25 public:
  26     /** Creates an `Optional` with the given value **/
  27     Optional(T);
  28
  29     /** Creates an `Optional` with the given value **/
  30     static Optional<T> create(T);
  31
  32     /** Checks whether this `Optional` contains a value **/
  33     bool isPresent() const;
  34
  35     /** Checks whether this `Optional` does not contain a value **/
  36     bool isEmpty() const;
  37
  38     /** Returns: The value if present **/
  39     T get();
  40
  41     bool hasValue(const T) const;
  42 };