jau::func::ylambda_target_t< R, L, A > Class Template Reference

func::ylambda_target_t is a Y combinator and deducing this implementation for lambda closures usable for recursive algorithms. More...

#include <functional.hpp>

Collaboration diagram for jau::func::ylambda_target_t< R, L, A >:

Public Types
typedef delegate_t< R, A... >	delegate_type

Static Public Member Functions
static delegate_type	delegate (L function) noexcept

Detailed Description

template<typename R, typename L, typename... A>
class jau::func::ylambda_target_t< R, L, A >

func::ylambda_target_t is a Y combinator and deducing this implementation for lambda closures usable for recursive algorithms.

The Y combinator allows passing the unnamed lambda instance itself, enabling recursive invocation from within the lambda.
In other words, a this reference of the unnamed lambda is passed to the lambda, similar to Deducing this.

The ylambda function<R(A...)> is invoked w/o explicitly passing the object parameter, as it is implicitly passed down to the user's lambda implementation.

Example implementing a recursive lambda factorial function

function<int(int)> f1 = function<int(int)>::bind_ylambda( [](auto& self, int x) -> int {
    if( 0 == x ) {
        return 1;
    } else {
        return x * self(x-1); // recursion, calling itself w/o explicitly passing `self`
    }
} );
assert( 24 == f1(4) ); // `self` is bound to delegate<R(A...)> `f.target`, `x` is 4
 
// or using explicit function<R(A...)>::delegate_type
 
function<int(int)> f2 = function<int(int)>::bind_ylambda( [](function<int(int)>::delegate_type& self, int x) -> int {
    if( 0 == x ) {
        return 1;
    } else {
        return x * self(x-1); // recursion, calling itself w/o explicitly passing `self`
    }
} );
assert( 24 == f2(4) ); // `self` is bound to function<int(int)>::delegate_type `f.target`, `x` is 4

An instance is identifiable as func::target_type::ylambda via jau::function<R(A...)>::type().

Template Parameters

R	function return type
L	typename holding the lambda closure
A	function arguments

See also

Function Overview

Deducing this

Explicit object parameter

Curiously Recurring Template Pattern

Examples

test_functional.hpp.

Definition at line 1005 of file functional.hpp.

Member Typedef Documentation

delegate_type

template<typename R , typename L , typename... A>

typedef delegate_t<R, A...> jau::func::ylambda_target_t< R, L, A >::delegate_type

Definition at line 1007 of file functional.hpp.

Member Function Documentation

delegate()

template<typename R , typename L , typename... A>

static delegate_type jau::func::ylambda_target_t< R, L, A >::delegate ( L  function )

inlinestaticnoexcept

Definition at line 1041 of file functional.hpp.

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The documentation for this class was generated from the following file:

• include/jau/functional.hpp