Haskell's Missing Concurrency Basics (2016)
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Haskell's Missing Concurrency Basics (2016)
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Re: Haskell's Missing Concurrency Basics (2016)
#2Thread-unsafe `println` is one of Clojure's quirks too!
Re: Haskell's Missing Concurrency Basics (2016)
#3Title is missing a (2016).
Re: Haskell's Missing Concurrency Basics (2016)
#4How does erlang/elixir do it? I've never really had any problems.
Re: Haskell's Missing Concurrency Basics (2016)
#5How does erlang/elixir do it? I've never really had any problems.
Elixir newbie here. If I remember correctly IO is implemented as a process, which means that different write requests are processed sequentially in the order they arrive to the process. The following link has more information: http://erlang.org/doc/apps/stdlib/io_protocol.html
Re: Haskell's Missing Concurrency Basics (2016)
#6Thread-unsafe `println` is one of Clojure's quirks too!
Interesting, I think it's thread-safe in Rust because one of the common performance improvements for console applications with lots of output is to acquire the relevant stream's lock (and perform all writes against a never-released guard) otherwise it's going to be acquired and dropped on every write: https://doc.rust-lang.org/src/std/io/stdio.rs.html#448-461
Re: Haskell's Missing Concurrency Basics (2016)
#7How does erlang/elixir do it? I've never really had any problems.
Elixir newbie here. If I remember correctly IO is implemented as a process, which means that different write requests are processed sequentially in the order they arrive to the process. The following link has more information: http://erlang.org/doc/apps/stdlib/io_protocol.html
Correct. Erlang (and therefore Elixir) stdio is implemented by means of sending messages to a process that does low-level writing to a console. When a single message is served, the other are queued up.
Therefore, when two processes (let's name them A and B) want to output something at the same time, the result is going to be AAAABBBB or BBBBAAAA (depending on the order in which the messages arrive in the mailbox), but never BBAABBAA or anything similar.
Re: Haskell's Missing Concurrency Basics (2016)
#8How does erlang/elixir do it? I've never really had any problems.
Elixir newbie here. If I remember correctly IO is implemented as a process, which means that different write requests are processed sequentially in the order they arrive to the process. The following link has more information: http://erlang.org/doc/apps/stdlib/io_protocol.html
It's very customary to let logging and such be done by a separate thread; this has also the benefit that the original (sending) thread can continue without waiting for the device.
Re: Haskell's Missing Concurrency Basics (2016)
#9Earlier quoted context omitted.
Elixir newbie here. If I remember correctly IO is implemented as a process, which means that different write requests are processed sequentially in the order they arrive to the process. The following link has more information: http://erlang.org/doc/apps/stdlib/io_protocol.html
Correct. Erlang (and therefore Elixir) stdio is implemented by means of sending messages to a process that does low-level writing to a console. When a single message is served, the other are queued up. Therefore, when two processes (let's name them A and B) want to output something at the same time, the result is going to be AAAABBBB or BBBBAAAA (depending on the order in which the messages arrive in the mailbox), bu…
...where "AAAA" and "BBBB" are two distinct messages, and not two sets of four messages each ("A", "A", "A", "A").
When I first read your example, it sounded like you were saying that the IO process would exhaust all messages from one source process before processing any messages from the other, no matter what order they arrived in.
Re: Haskell's Missing Concurrency Basics (2016)
#10Use an STM channel or some other lock and put your messages for the shared resource (the terminal ui) through that channel. There’s no way to automatically figure out what granularity the programmer expects from the output so make them specify. Haskell makes specifying that staggeringly easy compared to other languages.