tick

Add to your lein or boot dependencies:

Tick adds the concept of immutable timelines to java.time. A timeline is a lazy but orderered sequence of maps, each containing a java.time.ZonedDateTime entry (under the key :tick/date.

Timelines are easy to generate. One generator is periodic-seq, which generates a uniform series of times separated by a fixed period.

Timelines are sequences of ticks, and ticks are Clojure maps. Here’s one:

Timelines can be finite or, or of course, infinite so

to avoid eternal waits.

Multiple timelines can be interleaved into a consolidated timeline.

interleave-timelines takes any number of timelines and returns a conslidated time-ordered timeline. amalgamation.

Clojure’s map takes a function and applies it to every item in a sequence. Similarly, tick’s schedule takes a function and applies it to timelines.

Schedules can be run by starting them with a clock.

You can stop, pause and resume schedules too.

A type of schdule, useful for testing, can be created with simulate.

If you want to wait for a ticker to complete its journey over a timeline, deref the result of start.

At any time after starting a ticker you can find out its future timeline with remaining, while inspecting its clock with clock.

Most Clojure time libraries use clj-time, but tick uses java.time which means that it requires Java 8.

Java 8’s java.time API is both influenced by, and superior to, Joda Time. It is a modern immutable API that supports functional programming. Unless you’re stuck on Java 7 or ambivalent about library choice, you should be using java.time.

The 'flow of time' complicates our systems and we can simplify them if we separate the concept of a timeline from the 'flow' of time we perceive.

For more information, see the author’s talk at ClojuTRE-2016 on The Universe As A Value where he argues that time is a perception.

Tick is based on the same original idea as Chime. The motivation is to be able to view timelines of remaining times while the schedule is running. Thanks to James Henderson for his work on Chime.

In particular, special credit to Eric Evans for discovering Allen’s interval algebra and pointing out its potential usefulness.

See https://dzone.com/articles/why-you-shouldnt-use-quartz

The MIT License (MIT)

Copyright © 2016 JUXT LTD.

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