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In theory, this function could affect a global variable, call other non-runtime constant functions, etc. C++11 introduced the keyword constexpr, which allows the user to guarantee that a function or object constructor is a compile-time constant. [11] The above example can be rewritten as follows:
The names "lambda abstraction", "lambda function", and "lambda expression" refer to the notation of function abstraction in lambda calculus, where the usual function f (x) = M would be written (λx. M), and where M is an expression that uses x. Compare to the Python syntax of lambda x: M.
C++11 allowed lambda functions to deduce the return type based on the type of the expression given to the return statement. C++14 provides this ability to all functions. It also extends these facilities to lambda functions, allowing return type deduction for functions that are not of the form return expression;.
As of the 2011 revision, the C++ language also supports closures, which are a type of function object constructed automatically from a special language construct called lambda-expression. A C++ closure may capture its context either by storing copies of the accessed variables as members of the closure object or by reference.
Many languages, including Perl, Python, Ruby, Smalltalk, C++ (11+), C# and VB.NET (new versions) and most functional languages, support lambda expressions, unnamed functions with inline syntax, that generally acts as callbacks..
Since C++11, lambda function syntax can be used to specify to operation to be iterated inline, avoiding the need to define a named function. Here is an example of for-each iteration using a lambda function:
C++11 and later – via lambda expressions (see quicksort example above) [11] Eiffel – explicitly disallows nesting of routines to keep the language simple; does allow the convention of using a special variable, Result , to denote the result of a (value-returning) function
C++ doesn't have: PROC – first class nested functions (emulation due to local definitions of class types, which could be functors; also, C++11 has lambda functions), OP and PRIO – definable operator symbols and priorities, garbage collection (could be emulated with help of smart pointers), use before define,