Книга: Standard Template Library Programmer
logical_or
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logical_or<T>
Category: functors
Component type: type
Description
Logical_or<T> is a function object; specifically, it is an Adaptable Binary Predicate, which means it is a function object that tests the truth or falsehood of some condition. If f is an object of class logical_and<T> and x and y are objects of class T (where T is convertible to bool) then f(x,y) returns true if and only if either x or y is true. [1]
Example
Finds the first instance of either ' ' or 'n' in a string.
char str[MAXLEN];
…
const char* wptr = find_if(str, str + MAXLEN, compose2(logical_or<bool>(), bind2nd(equal_to<char>(), ' '), bind2nd(equal_to<char>(), 'n')));
assert(wptr == str + MAXLEN || *wptr == ' ' || *wptr == 'n');
Definition
Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h.
Template parameters
| Parameter | Description |
|---|---|
T |
The type of logical_or's arguments |
Model of
Adaptable Binary Predicate, DefaultConstructible
Type requirements
T must be convertible to bool.
Public base classes
binary_function<T, T, bool>
Members
| Member | Where defined | Description |
|---|---|---|
first_argument_type |
Adaptable Binary Function | The type of the first argument: T |
second_argument_type |
Adaptable Binary Function | The type of the second argument: T |
result_type |
Adaptable Binary Function | The type of the result: bool |
bool operator()(const T& x, const T& y) const |
Binary Function Function | call operator. The return value is x || y. |
logical_or() |
Default Constructible | The default constructor. |
New members
All of logical_or's members are defined in the Adaptable Binary Function and Default Constructible requirements. Logical_or does not introduce any new members.
Notes
[1] Logical_and and logical_or are not very useful by themselves. They are mainly useful because, when combined with the function object adaptor binary_compose, they perform logical operations on other function objects.
See also
The function object overview, logical_and, logical_not.
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