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Standard Template Library Programmer's Guide
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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	Default
`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.