User Guide

APLProcess starts a new Dyalog APL interpreter in another process. What that process does is entirely up to you. Common uses include:

• setting up a Remote Procedure Call (RPC) service to distribute processing load between multiple APL processes.
• delegating a long-running task to another APL process
• delegating processing to another APL process to reduce the potential impact of code failure. If the code running in another process fails, it's less likely to impact the processing in the current APL session.

Note

Currently APLProcess can start new APL processes only on the same platform. As most processors have multiple cores, this can still help distribute processing load and increase throughput. The ability to start new APL processes on other platforms using ssh is under development.

Terminology

Even though APLProcess is implemented as a Dyalog APL class, you do not need to know much about the object-oriented programming (OOP) features of Dyalog APL.

Instance

An "instance" of APLProcess is created when you call APLProcess.New or the use the ⎕NEW system function. Instances are independent of one another.

Method

In OOP terminology, APL functions within classes are called "methods". An individual method can either apply only to an instance (this is called an "instance method"), or to the class itself (this is called a "shared method").

Field or Setting

In OOP terminology, variables are called "fields", but for this documentation, we'll refer to them as "settings".

Throughout this document we will use the following terms with the following meanings:

Parent Process

This is the process from where APLProcess is used to start "child" processes.

Child Process

This is an APL process started by a "parent" process. Each child process has a reference back to the "parent" process in the form of a "parent process ID" (PPID).

p

An instance of APLProcess which is the result of running APLProcess.New or using ⎕NEW. Of course, you can use whatever name you prefer in your code.

Creating and starting APLProcess

There are three ways to create and run an instance of APLProcess.

Use ⎕NEW with constructor arguments

This will start an APL process and return an APLProcess instance.

      p←⎕NEW APLProcess ('/myApp' '' 0 'SERVE:*:4502')

Use ⎕NEW without constructor arguments

This will create and return an instance of APLProcess. You can then set whatever parameters you need and start the APL process using the Run method.

      p←⎕NEW APLProcess
      p.(Ws RideInit)←'/myApp' 'SERVE:*:4502'
      p.Run

Use APLProcess.New

APLProcess.New is a shared method that will create and return an instance of APLProcess, applying any arguments as parameters. You can then start the APL process using the Run method. Supplying '' as the argument to APLProcess.New is equivalent of using ⎕NEW APLProcess without any arguments.

      p←APLProcess.New '/myApp' '' 0 'SERVE:*:4502'
      p.Run

Stopping an APL Process

Use p.Kill to terminate the child APL process. p.kill will return 1 if the child process was successfully terminated, 0 otherwise.

Checking if an APL Process is Running

Use p.HasExited to check if a child process is running. p.HasExited will return 1 is the child process is not running and 0 if the child process is running.

Cross-Platform Functionality

To the extent possible, APLProcess presents a consistent API across all platforms on which Dyalog APL runs. This way you shouldn't have to change your application code that uses APLProcess if you're using multiple platforms.

Once the child process has been started, the APLProcess instance contains an object named Proc. Under Windows, Proc is an instance of the .NET System.Diagnostics.Process class. On non-Windows platforms, Proc is a namespace with elements named the same as a selected subset of the features of the .NET class.