Session Initialisation

Introduction

Each time Dyalog starts it loads and loads an initialisation file whose name is defined by the DyalogStartup parameter. The code defined in this file performs Session initialisation. If DyalogStartup is undefined, the system uses the first file it finds named StartupSession with file extension .aplf, .apln or .aplc in the Dyalog directory. If the file has the .aplf extension, it is executed. If it has a .apln or .aplc extension, the system instantiates the namespace or class and executes its Run function (if it exists).

At the end of the initialisation, the function defined by the .aplf file (or the Run function of the namespace or class) becomes the niladic function ⎕SE.StartupSession, which be called to re-run the session initialisation procedures.

Implementation

Code to be installed in ⎕SE is specified in APL source code files contained in Session initialisation directories identified by the DyalogStartupSE parameter. If this parameter is not specified, the default is a directory named StartupSession located in three standard locations as described below. See DyalogStartupSE.

Only content stored in files matching the wildcard patterns *.dyalog and *.apl? will be loaded. All such files must be appropriate for ⎕FIX.

For each sub-directory in a Session initialisation directory, a corresponding namespace is created in ⎕SE. Any source code files in these sub-directories will be fixed in their respective corresponding namespaces, and nested sub-directories become nested namespaces, recursively

Every top-level directory that is loaded as a namespace in ⎕SE can have a Run function which (depending on the value of the DyalogStartup_X parameter, will be called after everything has been loaded. This does not apply to sub-namespaces. See DyalogStartup_X.

This requires Link which is available by default. A custom version of Link can be used. See DyalogLink.

The Session initialisation directories are processed in alphabetical order and code defined in each directory will replace code with the same name defined previously. In effect, this means that user-supplied content can replace content supplied by Dyalog Ltd. and version-specific content can replace version-agnostic content.

Default Session Initialisation Directories

If the DyalogStartupSE parameter is undefined, APL looks for Session initialisation directories named StartupSession in the following three locations, and processes them in that order:

  1. The Dyalog installation directory (which contains the dyalog executable)
  2. A version-agnostic sub-directory in the user directory (the standard directory for user-related Dyalog APL files)
  3. A version-specific sub-directory in the user directory, whose name is derived as described below.

Under Windows these might be:

  1. C:\Program Files\Dyalog\Dyalog APL-64 19.0 Unicode
  2. C:\Users\Pete\Documents\Dyalog APL Files
  3. C:\Users\Pete\Documents\Dyalog APL-64 19.0 Unicode Files

The version-specific name is :

     Dyalog APL{bit} {version} {edition}

where: