Clock

Flix provides Clock as a library effect for querying the current wall-clock time. The Clock effect has a default handler, so no explicit runWithIO call is needed in main. The key module is Time.Clock.

The Clock Effect

The Clock effect has a single operation that returns the time since the epoch in a given unit:

pub eff Clock {
    /// Returns a measure of time since the epoch in the given time unit `u`.
    def currentTime(u: TimeUnit): Int64
}

The TimeUnit enum determines the granularity of the result:

pub enum TimeUnit with Eq, ToString {
    case Days,
    case Hours,
    case Microseconds,
    case Milliseconds,
    case Minutes,
    case Nanoseconds,
    case Seconds
}

Reading the Current Time

The simplest use of Clock is to read the current time and print it:

use Time.Clock
use Time.TimeUnit

def main(): Unit \ { Clock, IO } =
    let timestamp = Clock.currentTime(TimeUnit.Milliseconds);
    println("${timestamp} ms since the epoch")

Because Clock has a default handler, the effect is handled automatically.

The now Function

The Clock.now function is a shorthand for Clock.currentTime(TimeUnit.Milliseconds):

use Time.Clock

def main(): Unit \ { Clock, IO } =
    let before = Clock.now();
    // ... do some work ...
    let after = Clock.now();
    println("Elapsed: ${after - before} ms")