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Filters

where

Appends a filter to the range, dropping elements that don't satisfy a specific predicate.

predicate must be a function f that takes the range's element x and returns a value indicating whether the condition is satisfied, i.e. \(f(x) \mapsto bool\).

Signature
template <typename TPredicate>
constexpr auto where( TPredicate&& predicate ) const;
Example
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const auto people = std::vector{
    Person{ .name = "Person 1", .age = 20 },
    Person{ .name = "Person 2", .age = 21 },
    Person{ .name = "Person 3", .age = 22 },
};

const auto query = linq::from( &people )
                  .where( []( const Person& p ) { return p.age > 20; } );

//               = Person 2, Person 3