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36 lines
836 B
Plaintext
36 lines
836 B
Plaintext
[#async_for]
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== cobalt/async_for.hpp
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For types like generators a `BOOST_COBALT_FOR` macro is provided, to emulate an `for co_await` loop.
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[source,cpp]
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----
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cobalt::generator<int> gen();
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cobalt::main co_main(int argc, char * argv[])
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{
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BOOST_COBALT_FOR(auto i, gen())
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printf("Generated value %d\n", i);
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co_return 0;
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}
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----
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The requirement is that the <<awaitable,awaitable>> used in the for loop has an `operator bool` to check if it
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can be awaited again. This is the case for <<generator, generator>> and <<promise,promise>>.
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That is, `BOOST_COBALT_FOR(__expression__, __declaration__) __statement__` the above statement is roughly equivalent to:
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[source,cpp,subs=+quotes]
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----
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{
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auto && __aw__ = co_await __expression__;
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while (__aw__)
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{
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__expression__ = co_await __aw__;
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__statement__
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}
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}
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---- |