3.3.1 Extension Use

As described in the beginning of this chapter, an extension is a Cogsys "plugin" that provides some extra functionality. In Cogsys 3.x, all of the included extensions draw pictures. They are loaded into Cogsys lists are truntime by the `%X' command (see section Load External Routine). They are used in Cogsys teslists by calling the `%I' command (see section Create Pictures from CXR).

It is important to note that the `%I' command takes one required argument (the number of pictures to create) and has one optional requirement, the preimage specification. After those arguments are parsed, the rest of the information in a `%I' command is passed directly to the extension. The extension does not (and can not) know about the `%I' arguments, because it is independent of the call mechanism. In the documentation that follows, arguments are numbered naturally, from 1; but it is important to understand that the nth extension argument might be the (n+1)th or (n+2)th argument in a `%I' call.

Syntax synposes are given like this:

EXTENSION arg1 arg2 ...