ref: 23c8f3f9409d2826a94277464125872319156911
dir: /Channels/README.md/
# Channels Limbo supports concurrent communication and synchronization between processes via channels and a few structures working in tandem with channels. The design for channels is inspired primarily by "Communicating Sequential Processes" (CSP) by Tony Hoare. Further reading on CSP: http://www.usingcsp.com/cspbook.pdf ## Source ### chans.b:33,36 This statement shows three channels being made. `done` is an unbuffered channel which transports integer values. `msgChan` is an unbuffered channel, instantiated using buffered channel syntax, which transports strings. `numChan` is a buffered channel which transports a tuple representing an integer pair. ### chans.b:38 The `spawn` statement is used to create a new process running a given function, in this case `summer()`. ### chans.b:40,45 This section loads number pairs from the variable `i` and the number 2 from 0 to 14, covering 15 total iterations. After the iterative statement completes, a (later discarded) value is passed to the channel `done`. The first (and only) value in `msgChan` is then read out and printed. Note: Writing to a channel whose buffer (or lack thereof) is currently full is a blocking operation. Similarly, reading from a channel whose buffer (or lack thereof) is currently empty is a blocking operation. ### chans.b:13,28 The function `summer()` operates an infinite loop which operates a single `alt` statement which is similar to a switch-case statement which operates on the presence of values within a channel. The three channels are used to coordinate operation between the two processes. `num` is checked first and a tuple of values is pulled out: a value and a power to raise said value to. The `n^p` operation is shown as `n**p` in Limbo, with the result being added to sum's current value. `done` is checked after `num` has no more values in its buffer. If a value is found, the sum is stringified and passed down `msg` and the looping condition is unset. The default value, indicated by `*=>`, is used when no channels have a value, so we sleep the current process for 5ms to de-schedule ourselves in case some form of scheduling is holding up our communications. ## Demo ; limbo chans.b ; chans Sum: 0 Sum: 1 Sum: 5 Sum: 14 Sum: 30 Sum: 55 Sum: 91 Sum: 140 Sum: 204 Sum: 285 Sum: 385 Sum: 506 Sum: 650 Final sum: 650 ; ## Exercises - Can you pass an ADT over a channel? - What happens if you pass a `ref` type over a channel?