1 //===-- Optional.h - Simple variant for passing optional values ---*- C++ -*-=// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file provides Optional, a template class modeled in the spirit of 11 // OCaml's 'opt' variant. The idea is to strongly type whether or not 12 // a value can be optional. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #ifndef LLVM_ADT_OPTIONAL 17 #define LLVM_ADT_OPTIONAL 18 19 #include <cassert> 20 21 namespace llvm { 22 23 template<typename T> 24 class Optional { 25 T x; 26 unsigned hasVal : 1; 27 public: Optional()28 explicit Optional() : x(), hasVal(false) {} Optional(const T & y)29 Optional(const T &y) : x(y), hasVal(true) {} 30 create(const T * y)31 static inline Optional create(const T* y) { 32 return y ? Optional(*y) : Optional(); 33 } 34 35 Optional &operator=(const T &y) { 36 x = y; 37 hasVal = true; 38 return *this; 39 } 40 getPointer()41 const T* getPointer() const { assert(hasVal); return &x; } getValue()42 const T& getValue() const { assert(hasVal); return x; } 43 44 operator bool() const { return hasVal; } hasValue()45 bool hasValue() const { return hasVal; } 46 const T* operator->() const { return getPointer(); } 47 const T& operator*() const { assert(hasVal); return x; } 48 }; 49 50 template<typename T> struct simplify_type; 51 52 template <typename T> 53 struct simplify_type<const Optional<T> > { 54 typedef const T* SimpleType; 55 static SimpleType getSimplifiedValue(const Optional<T> &Val) { 56 return Val.getPointer(); 57 } 58 }; 59 60 template <typename T> 61 struct simplify_type<Optional<T> > 62 : public simplify_type<const Optional<T> > {}; 63 64 /// \brief Poison comparison between two \c Optional objects. Clients needs to 65 /// explicitly compare the underlying values and account for empty \c Optional 66 /// objects. 67 /// 68 /// This routine will never be defined. It returns \c void to help diagnose 69 /// errors at compile time. 70 template<typename T, typename U> 71 void operator==(const Optional<T> &X, const Optional<U> &Y); 72 73 /// \brief Poison comparison between two \c Optional objects. Clients needs to 74 /// explicitly compare the underlying values and account for empty \c Optional 75 /// objects. 76 /// 77 /// This routine will never be defined. It returns \c void to help diagnose 78 /// errors at compile time. 79 template<typename T, typename U> 80 void operator!=(const Optional<T> &X, const Optional<U> &Y); 81 82 /// \brief Poison comparison between two \c Optional objects. Clients needs to 83 /// explicitly compare the underlying values and account for empty \c Optional 84 /// objects. 85 /// 86 /// This routine will never be defined. It returns \c void to help diagnose 87 /// errors at compile time. 88 template<typename T, typename U> 89 void operator<(const Optional<T> &X, const Optional<U> &Y); 90 91 /// \brief Poison comparison between two \c Optional objects. Clients needs to 92 /// explicitly compare the underlying values and account for empty \c Optional 93 /// objects. 94 /// 95 /// This routine will never be defined. It returns \c void to help diagnose 96 /// errors at compile time. 97 template<typename T, typename U> 98 void operator<=(const Optional<T> &X, const Optional<U> &Y); 99 100 /// \brief Poison comparison between two \c Optional objects. Clients needs to 101 /// explicitly compare the underlying values and account for empty \c Optional 102 /// objects. 103 /// 104 /// This routine will never be defined. It returns \c void to help diagnose 105 /// errors at compile time. 106 template<typename T, typename U> 107 void operator>=(const Optional<T> &X, const Optional<U> &Y); 108 109 /// \brief Poison comparison between two \c Optional objects. Clients needs to 110 /// explicitly compare the underlying values and account for empty \c Optional 111 /// objects. 112 /// 113 /// This routine will never be defined. It returns \c void to help diagnose 114 /// errors at compile time. 115 template<typename T, typename U> 116 void operator>(const Optional<T> &X, const Optional<U> &Y); 117 118 } // end llvm namespace 119 120 #endif 121