blob: 70d351c5fdb8608cca125f6016506945836ef177 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
/******************************************************************************
* Top contributors (to current version):
* Tim King, Mathias Preiner
*
* This file is part of the cvc5 project.
*
* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
* in the top-level source directory and their institutional affiliations.
* All rights reserved. See the file COPYING in the top-level source
* directory for licensing information.
* ****************************************************************************
*
* This provides a templated Maybe construct.
*
* This class provides a templated Maybe<T> construct.
* This follows the rough pattern of the Maybe monad in haskell.
* A Maybe is an algebraic type that is either Nothing | Just T
*
* T must support T() and operator=.
*
* This has a couple of uses:
* - There is no reasonable value or particularly clean way to represent
* Nothing using a value of T
* - High level of assurance that a value is not used before it is set.
*/
#include "cvc4_public.h"
#ifndef CVC5__UTIL__MAYBE_H
#define CVC5__UTIL__MAYBE_H
#include <ostream>
#include "base/exception.h"
namespace cvc5 {
template <class T>
class Maybe
{
public:
Maybe() : d_just(false), d_value(){}
Maybe(const T& val): d_just(true), d_value(val){}
Maybe& operator=(const T& v){
d_just = true;
d_value = v;
return *this;
}
inline bool nothing() const { return !d_just; }
inline bool just() const { return d_just; }
explicit operator bool() const noexcept { return just(); }
void clear() {
if(just()){
d_just = false;
d_value = T();
}
}
const T& value() const
{
if (nothing())
{
throw Exception("Maybe::value() requires the maybe to be set.");
}
return d_value;
}
private:
bool d_just;
T d_value;
};
template <class T>
inline std::ostream& operator<<(std::ostream& out, const Maybe<T>& m){
out << "{";
if(m.nothing()){
out << "Nothing";
}else{
out << "Just ";
out << m.value();
}
out << "}";
return out;
}
} // namespace cvc5
#endif /* CVC5__UTIL__MAYBE_H */
|
