Message passing pattern matching

[Casper Færgemand]

Hey, I'm handling concurrency with message passing, previously 
with D's concurrency, now with Vibe-d, which I assume works the 
same way.


My app is a chat server, and when a connection is opened to a 
client, I store the Tid of the thread (or fibre?) handling 
sending messages out to the client. This lets me broadcast 
messages to all Tids. When a connection is closed, the thread 
requests that its Tid is removed from the list.


Both adding and removing the Tid technically require only the Tid 
to be message passed. However, I would like to distinguish 
between the two cases. I currently have two empty structs named 
AddTid and RemoveTid, and I pass those along. I assume some bytes 
must be passed in their place to tell of their type, but that's 
fine.


It does feel rather hacked, however. I'm aware that D doesn't 
support excessively fancy pattern matching, like what is found in 
SML, but is there a more correct way to do this? Enums don't 
work, because they have the same type. I can pattern match the 
enums later, but I want to do it immediately.

Re: Message passing pattern matching

[Casper Færgemand]

A small example:

while (true) {
  receive(
(Tid tid, AddTid _) {some code}
(Tid tid, RemoveTid _) {some other code}
(string s) {broadcast stuff}
  )
}

struct AddTid {}
struct RemoveTid {}

Re: Message passing pattern matching

[Stanislav Blinov]

On Wednesday, 29 January 2014 at 21:50:28 UTC, Casper Færgemand 
wrote:

A small example:

while (true) {
  receive(
(Tid tid, AddTid _) {some code}
(Tid tid, RemoveTid _) {some other code}
(string s) {broadcast stuff}
  )
}

struct AddTid {}
struct RemoveTid {}


From where I sit that's a perfectly fine approach. After all, you 
do want to distinguish your own message types: any other 
std.concurrency-aware code (i.e. library) could pass its own 
messages. You wouldn't want to mistake those for your own private 
communication protocol.