xtd::expressions::placeholder< index > Struct Template Reference

Inheritance diagram for xtd::expressions::placeholder< index >:

Definition

template<size_t index>
struct xtd::expressions::placeholder< index >

The xtd::expressions::placeholder object is placeholder for all expressions.

Namespace

xtd::expressions

Header

#include <xtd/expressions/placeholder>

Library

xtd.core

Remarks

Prefer the xtd::expressions::arg <N> or xtd::expressions::_, xtd::expressions::_1 ... xtd::expressions::_10 instead xtd::expressions::placeholder.

Examples

The following example shows how to use xtd::expressions::expression::placeholder.

#include <xtd/xtd>
 
auto main() -> int {
  // auto placeholder1 = [](auto&& _) {return _;};
  auto placeholder1 = _;
  println("placeholder1 result => {}", placeholder1(10));
  auto placeholder2 = _1;
  println("placeholder2 result => {}", placeholder2(10));
  auto placeholder3 = placeholder<1> {};
  println("placeholder3 result => {}", placeholder3(10));
  auto placeholder4 = expression::placeholder<1>();
  println("placeholder4 result => {}", placeholder4(10));
  println();
  // auto expr1 = [](auto&& _1, auto&& _2, auto&& _3) {return _1 + _2 + _3;};
  auto expr1 = _1 + placeholder<2> {} + expression::placeholder<3>();
  println("expr1 result => {}", expr1(10, 20, 30));
}
 
// This code produces the following output :
//
// placeholder1 result => 10
// placeholder2 result => 10
// placeholder3 result => 10
// placeholder4 result => 10
//
// expr1 result => 60

Public Fields
static constexpr operator_precedence	precedence
	The operator precedence. That contains one of xtd::expressions::operator_precedence values.

Public Operators
template<typename... args_t>
constexpr decltype(auto)	operator() (args_t &&... args) const
	Gets the placeholder value.

Additional Inherited Members

Member Function Documentation

operator()()

template<size_t index>

template<typename... args_t>

decltype(auto) xtd::expressions::placeholder< index >::operator() ( args_t &&... args ) const

inlineconstexpr

Gets the placeholder value.

Returns

The placeholder value.

Member Data Documentation

precedence

template<size_t index>

operator_precedence xtd::expressions::placeholder< index >::precedence

staticconstexpr

The operator precedence. That contains one of xtd::expressions::operator_precedence values.

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

• xtd.core/include/xtd/expressions/placeholder.hpp