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(Note that these are not member functions.)
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| constexpr tribool | operator&& (const tribool &lhs, const tribool &rhs) noexcept |
| | Computes the logical and of two tribool. More...
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| constexpr tribool | operator|| (const tribool &lhs, const tribool &rhs) noexcept |
| | Computes the logical or of two tribool. More...
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| template<typename CharT > |
| constexpr const CharT * | get_default_indeterminate_name () noexcept |
| | Returns the default indeterminate name. More...
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| template<typename CharT , typename Traits > |
| auto | operator<< (std::basic_ostream< CharT, Traits > &out, const tribool &tri) -> decltype(out) |
| | Outputs the value of the tribool to the stream provided. More...
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| template<typename CharT , typename Traits > |
| auto | operator>> (std::basic_istream< CharT, Traits > &in, tribool &tri) -> decltype(in) |
| | Reads a tribool value from an input stream. More...
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Implements Kleene's logic for three-state booleans. This class should be preferred to gears::utility::maybe<bool> as it implements true three-state logic. The three states for the boolean are true, false, and indeterminate. So for example all three are valid:
namespace util = gears::utility;
util::tribool x = true;
x = false;
The input and output operators are supported by default. In order to disable it, you have to define the macro GEARS_NO_IOSTREAM. The input/output operators behave similarly to bool values, except indeterminate can be read or output as 2. When std::boolalpha is active, they can be read and written in the same similar manner except the default string would be "indeterminate". For example:
namespace util = gears::utility;
std::cout << std::boolalpha << x << '\n';
Output:
indeterminate
You can change the indeterminate value through instantiating a value of type indeterminate_t. Likewise, you can change the default string read or written through the use of the indeterminate_name facet. For example:
namespace util = gears::utility;
constexpr util::indeterminate_t null{};
util::tribool x = null;
std::locale myloc(std::cout.getloc(), new util::indeterminate_name<char>("null"));
std::cout.imbue(myloc);
std::cout << std::boolalpha << x << '\n';
Output:
null
Definition at line 99 of file tribool.hpp.
template<typename CharT , typename Traits >
| auto operator<< |
( |
std::basic_ostream< CharT, Traits > & |
out, |
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const tribool & |
tri |
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) |
| -> decltype(out) |
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related |
Outputs the value of the tribool to the stream provided.
The value written when std::boolalpha is not active is as follows:
| internal value | output |
false | 0 |
true | 1 |
indeterminate | 2 |
If std::boolalpha is written then the name written to depends on the facet provided. The true and false values are provided by the std::numpunct functions that implement do_truename and do_falsename. The indeterminate value is provided by the indeterminate_name facet.
Assuming everything is defaulted, the values written are as follows:
| internal value | output |
false | "false" |
true | "true" |
indeterminate | "indeterminate" |
This operator overload is only available if GEARS_NO_IOSTREAM is not defined.
- Parameters
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| out | Output stream to write to. |
| tri | Tribool to read from. |
- Returns
- The output stream.
Definition at line 381 of file tribool.hpp.
template<typename CharT , typename Traits >
| auto operator>> |
( |
std::basic_istream< CharT, Traits > & |
in, |
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tribool & |
tri |
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) |
| -> decltype(in) |
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related |
Reads a tribool value from an input stream. This function works similarly to the output stream except inverted. That is, if std::boolalpha is not active, then the values of 0, 1, and 2 will set the tribool appropriately otherwise failure will be set.
If std::boolalpha is set then the string is read from the appropriate facets. Which are std::numpunct for true and false and indeterminate_name for the indeterminate value.
This operator overload is only available if GEARS_NO_IOSTREAM is not defined.
- Parameters
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| in | The input stream to read from. |
| tri | The tribool to place the value to. |
- Returns
- The input stream.
Definition at line 425 of file tribool.hpp.
