Книга: Standard Template Library Programmer

logical_and

logical_and<T>

Category: functors

Component type: type

Logical_and<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 both x and y are true. [1]

Finds the first element in a list that lies in the range from 1 to 10.

list<int> L;
…
list<int>::iterator in_range = find_if(L.begin(), L.end(), compose2(logical_and<bool>(), bind2nd(greater_equal<int>(), 1), bind2nd(less_equal<int>(), 10)));
assert(in_range == L.end() || (*in_range >= 1 && *in_range <= 10));

Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h.

Adaptable Binary Predicate, DefaultConstructible

T must be convertible to bool.

binary_function<T, T, bool>

All of logical_and's members are defined in the Adaptable Binary Function and Default Constructible requirements. Logical_and does not introduce any new members.

[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.

The function object overview, logical_or, logical_not.

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