Generator< T > Class Template Reference

#include <Pt/Generator.h>

Represents a coroutine that yields a sequence of values and may itself co_await. More...

Inherits AwaiterBase.

Classes
class	NextAwaiter
	Provides the awaitable returned by Generator::next(). More...

Public Member Functions
	Generator (handle_type h)
	Constructs a generator that takes ownership of h.
	Generator (Generator &&other) noexcept
	Moves the coroutine frame from other.
	~Generator ()
	Cancels the generator if it still owns a coroutine frame.
void	cancel () override
	Cancels the generator. More...
NextAwaiter	next ()
	Returns an awaitable that produces the next value. More...
T	value ()
	Returns the last yielded value. More...

Detailed Description

template<typename T>
class Pt::Generator< T >

A Generator produces values lazily with co_yield. Unlike a synchronous generator, its body may also co_await.

Consume a generator from a Task. Await Generator::next() until it returns false and read each value with Generator::value().

A Generator is move-only and owns the coroutine frame. Generator<T&> yields a reference. That object must remain valid until the next Generator::next() or until the generator is destroyed.

Only one Generator::next() may be pending. Awaiting next() while another next() is already pending throws std::logic_error.

Exceptions that leave the coroutine body are rethrown from the Generator::next() await.

The following task sums the values of a generator:

Pt::Generator<int> squares(int n)
{
    for(int i = 1; i <= n; ++i)
        co_yield i * i;
}
 
Pt::Task<int> sumSquares(int n)
{
    auto gen = squares(n);
    int sum = 0;
 
    while( co_await gen.next() )
        sum += gen.value();
 
    co_return sum;
}

Member Function Documentation

cancel()

void cancel ( )

overridevirtual

Aborts the pending awaitable, if any, detaches an in-flight next() await, and destroys the coroutine frame.

Implements AwaiterBase.

next()

NextAwaiter next

(

)

co_await of the result is true while a value is available. Use Generator::value() to read that value.

value()

T value

(

)

Valid after a co_await of Generator::next() returned true.