technote016.md

Tech Note 016 - Command parameters, context, argc/argv, the clipboard, messages, and namespaces in IO

Provide a unified namespace for multi-language programming and user interaction in IO

• At command invocation time, whether on click or in a command script or on receipt of a message: 1 Available modules (loaded or not) provide a namespace for commands in the text user interface and command scripts and message sends 2 The modules namespace is a linear concatenation of Module.Command(s) 3 bin paths or union mounts per context can tailor the modules visible in the namespace (linear per context) 4 independent instances of modules on import can tailor the behavior of the visible modules per importing module 5 There may be relevent UI state (selected text, marker positions, clipboard stack of content) 6 There may be relevent environment values (per context) 7 There may be open streams for input and output and error

• At compile time 1

• something 1 saving a referenced global variable on the stack upon procedure entry 2 accessing and modifying the global variable as usual 3 restoring the cached value upon procedure exit

• A DYN keyword and compiler assistance can reduce boilerplate

• DYN variables may enable the common lisp condition system in Oberon

• This kind of dynamic scope may only work local to the thread of execution

• This kind of dynamic scope is ineficient for large objects