Concurrency

Background

Given a file named “pen.json” with:

{
  "type": "application",
  "dependencies": {
    "Os": "pen:///os"
  }
}

Use spawn function

Given a file named “main.pen” with:

main = \(ctx context) none {
  f = go(\() none { none })

  f()
}

When I successfully run pen build

Then I successfully run ./app.

Use race function

Given a file named “main.pen” with:

import Os'Process

main = \(ctx context) none {
  xs = race([[none] [none none]])

  if [x, ...xs] = xs {
    x()
  } else {
    Process'Exit(ctx.Os, 1)
  }
}

When I successfully run pen build

Then I successfully run ./app.

Use race function with multiple lists

Given a file named “main.pen” with:

import Os'Process

main = \(ctx context) none {
  xs = race([[none] [none none], [none none]])

  if [x, ...xs] = xs {
    x()
  } else {
    Process'Exit(ctx.Os, 1)
  }
}

When I successfully run pen build

Then I successfully run ./app.

Use race function to get the first result

Given a file named “main.pen” with:

import Os'Context { Context }
import Os'Process
import Os'Time

main = \(ctx context) none {
  xs = race([[boolean]
    [boolean (\() boolean { loop(ctx.Os) false })()],
    [boolean true],
  ])

  if [x, ...xs] = xs {
    if x() {
      none
    } else {
      Process'Exit(ctx.Os, 1)
    }
  } else {
    Process'Exit(ctx.Os, 1)
  }
}

loop = \(ctx Context) none {
  Time'Sleep(ctx, 1)
  loop(ctx)
}

When I successfully run pen build

Then I successfully run ./app.

Use race function and get all elements

Given a file named “main.pen” with:

import Os'Process

main = \(ctx context) none {
  xs = race([[none] [none none], [none none]])

  if xs == [none none, none] {
    none
  } else {
    Process'Exit(ctx.Os, 1)
  }
}

When I successfully run pen build

Then I successfully run ./app.