simple usage of transform & sync_wait with compile error

[zeyangl]

I tried writing a shortest unifex example possible and came up with this

I'm curious as why sync_wait is not compiling. The error is a bit too obfiscated for someone not very familiar with unifex yet. If I return void from the second function it works fine. After inspecting transform's definition it seems to allow returning custom values.

I'm using vcpkg's version of unifex(when "then" is still "transform"), and in visual studio 2019.

Thanks.

[RishabhRD]

I am not an expert but, I don't know if [](){} is even a sender. You can try:

  auto cc = then(just(), [] { return 0; });
  auto x = sync_wait(cc);
  EXPECT_EQ(x.value(), 0);

You can use transform if you are using that version. As of my limited knowledge, just() is a sender that just completes by calling set_value() with no arguments (If just is called with arguments it would call set_value with those arguments). So, it should serve your purpose.

[zeyangl]

Thanks. I thought the lambda could be implicitly packaged as a sender. I went through the unit tests and found them to be very helpful learning the patterns.

[kirkshoop]

@RishabhRD is correct.
Thanks for the question and the answer!

[zeyangl]

It might be helpful to point readers to the unit tests from the docs, better than examples for initial learning. It's been 2 days and I just realized that's where I should look first.