std::ranges:: views:: iota, std::ranges:: iota_view

Customization point objects

The name views::iota denotes a customization point object , which is a const function object of a literal semiregular class type. For exposition purposes, the cv-unqualified version of its type is denoted as __iota_fn .

All instances of __iota_fn are equal. The effects of invoking different instances of type __iota_fn on the same arguments are equivalent, regardless of whether the expression denoting the instance is an lvalue or rvalue, and is const-qualified or not (however, a volatile-qualified instance is not required to be invocable). Thus, views::iota can be copied freely and its copies can be used interchangeably.

Given a set of types Args... , if std:: declval < Args > ( ) ... meet the requirements for arguments to views::iota above, __iota_fn models

• std:: invocable < __iota_fn, Args... > ,
• std:: invocable < const __iota_fn, Args... > ,
• std:: invocable < __iota_fn & , Args... > , and
• std:: invocable < const __iota_fn & , Args... > .
  

Otherwise, no function call operator of __iota_fn participates in overload resolution.

Data members

Member functions

Deduction guides

Nested classes

Helper templates

This specialization of ranges:: enable_borrowed_range makes iota_view satisfy borrowed_range .

Example

#include <algorithm>
#include <iostream>
#include <ranges>
 
struct Bound
{
    int bound;
    bool operator==(int x) const { return x == bound; }
};
 
int main()
{
    for (int i : std::ranges::iota_view{1, 10})
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (int i : std::views::iota(1, 10))
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (int i : std::views::iota(1, Bound{10}))
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (int i : std::views::iota(1) | std::views::take(9))
        std::cout << i << ' ';
    std::cout << '\n';
 
    std::ranges::for_each(std::views::iota(1, 10),
                          [](int i){ std::cout << i << ' '; });
    std::cout << '\n';
}

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Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also