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This documentation is very much a work in progress. Expected completion is November 2022.


Jarvis is an HTTP server that makes it easy to create a web service to provide access to your APL code from the web or a local network.

Any client program written in any language on any platform that can process HTTP requests can access a Jarvis-based web service. This vastly increases the potential audience for your application - the client can be a standard web browser, a phone app, a browser-based app, or a custom client written in a language like Python or C# and yes, even APL.

The name Jarvis is a pseudo-acronym for JSON and REST Service ("vice" becomes "vis") and was also inspired by J.A.R.V.I.S. (Just A Rather Very Intelligent System) from the Marvel Cinematic Universe.

Design Goals

Jarvis is designed to make it very easy for an APLer to create web services without requiring in-depth knowledge of web service frameworks. In designing Jarvis we've attempted to

  • Make Jarvis' default behavior simple and applicable to many use cases
  • Make few assumptions about what the user actually needs to do
  • Provide hooks to allow the user to tailor or extend Jarvis' behavior if needed

Create an APL Web Service in 5 Minutes

If you know how to write a monadic, result-returning APL function, you're ready to run your first Jarvis-based web service. Here's how:

  1. If you already have a copy of the Jarvis class, skip to step 3. Otherwise, load the HttpCommand utility so that we can download a copy of Jarvis and also use HttpCommand for testing our web service.

          ]load HttpCommand
  2. Next, download a copy of Jarvis. Note, the following statement simply downloads the latest, perhaps pre-release, version of the Jarvis class for this quick demonstration. For a production environment, you should use a released version of Jarvis. HttpCommand.Fix both downloads and runs ⎕FIX on an APL code file from the web.

          HttpCommand.Fix '
  3. Write one or more monadic, result-returning APL functions. For instance:

          )cs #
          sum ← {+/⍵}                       ⍝ dfns work
          total ← +/                        ⍝ derived functions work
          ⎕FX '∇r←addemup a' 'r←+/a' '∇'    ⍝ and of course, tradfns work
  4. You can now run your web service running on port 8080 and serving code from the # (root) namespace.

          (server rc)←Jarvis.Run 8080 #
    2021/11/22 @ 15:12:06 - Conga copied from C:\Program Files\Dyalog\Dyalog APL-64 18.2 Unicode/ws/conga
    2021/11/22 @ 15:12:06 - Local Conga reference is #.Jarvis.[LIB]
    2021/11/22 @ 15:12:06 - Jarvis started in "JSON" mode on port 8080
    2021/11/22 @ 15:12:06 - Serving code in #
    2021/11/22 @ 15:12:06 - Click http://localhost:8080 to access web interface

If the server started successfully, you'll see messages similar to those above and server will be a reference to the server instance and the return code rc should be 0.

Now, let's test our service using Jarvis' built-in HTML interface. You could click on the link displayed or open your favorite browser to http://localhost:8080, but just for fun, we'll use Dyalog's HTMLRenderer object.

       'h' ⎕WC 'HTMLRenderer' ('URL' 'localhost:8080')

Jarvis Sample

We select the Endpoint (APL function) we want from the drop down list, enter some valid JSON data ([1,3,5]), and press Send to send the request to Jarvis. Jarvis' response is then sent back and displayed.

We can also use HttpCommand to call the web service.

      (url data headers)←'localhost:8080/total' '[1,3,5]' ('content-type' 'application/json')
      (HttpCommand.Do 'POST' url data headers).Data

We can use the cURL command to call the web service.

C:\> curl -H "content-type: application/json" -X POST -d [1,3,5] http://localhost:8080/addemup

To stop the service, simply type server.stop

Interested? Read on...