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The following is a declaration of the concept "equality_comparable" from the <concepts> header of a C++20 standard library. This concept is satisfied by any type T such that for lvalues a and b of type T, the expressions a==b and a!=b as well as the reverse b==a and b!=a compile, and their results are convertible to a type that satisfies the concept "boolean-testable":
The three-way comparison operator or "spaceship operator" for numbers is denoted as <=> in Perl, Ruby, Apache Groovy, PHP, Eclipse Ceylon, and C++, and is called the spaceship operator. [2] In C++, the C++20 revision adds the spaceship operator <=>, which returns a value that encodes whether the 2 values are equal, less, greater, or unordered ...
In Lisp family languages such as Common Lisp, Scheme, and others, functions are objects, just like strings, vectors, lists, and numbers. A closure-constructing operator creates a function object from a part of the program: the part of code given as an argument to the operator is part of the function, and so is the lexical environment: the ...
Compare with the using statement which requires the resource to implement the System.IDisposable interface. [5]) The Nim programming language implements concepts as a series of arbitrary compile-time boolean predicates. [6] Another language implementing something very similar to concepts is Haskell, where the feature is called type classes.
In the C++ programming language, special member functions [1] are functions which the compiler will automatically generate if they are used, but not declared explicitly by the programmer. The automatically generated special member functions are: Default constructor if no other constructor is explicitly declared.
The algorithms provided by the C++ Standard Library do not require function objects of more than two arguments. Function objects that return Boolean values are an important special case. A unary function whose return type is bool is called a predicate , and a binary function whose return type is bool is called a binary predicate .
Notice that the type of the result can be regarded as everything past the first supplied argument. This is a consequence of currying, which is made possible by Haskell's support for first-class functions; this function requires two inputs where one argument is supplied and the function is "curried" to produce a function for the argument not supplied.
A class in C++ is a user-defined type or data structure declared with any of the keywords class, struct or union (the first two are collectively referred to as non-union classes) that has data and functions (also called member variables and member functions) as its members whose access is governed by the three access specifiers private, protected or public.