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Comment by IpV8 | Hacker News Reader

That built in lag is so incredibly miniscule in the grand scheme of programming that 99.9999% of times it will not matter, and if it does you are using C or Assembly anyways.

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That argument applies to the example of the abstraction, not the abstraction itself.

No, readLine will block until a line is available.

Consider a command line IM app using pipes to communicate to the server (just to roll with the readLine example). User 1 has not typed anything, so their file is empty. User 2 has typed a bunch of stuff.

    user1line = readLine "user1file.pipe"
    user2line = readLine "user2file.pipe"
    getFirstAvailableFutureAndProcess [user1line, user2line] processorFunc

What you want this to do is handle whichever user types something first. In reality it will only process user1line.

Boost.ASIO (and the corresponding C++ network TR proposal) uses HKTs to select the wait strategy (i.e. coroutines, futures, plain callbacks or whatever the user prefers) with minimal overhead.

No, it matters. Inefficiency adds up, and CPU cycles you waste on useless overhead aren't available to spend on something that actually matters -- like Garbage Collection.

It matters a lot if you are relying on asynchronous semantics. You risk deadlock if the request blocks.

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