The New Module System

New

Caution

The new module system is a work in progress. Not all features mentioned have been (fully) implemented

STELF’s old module system, outside of standard ML, is quite weak. The new module system is designed to be a true module system, which not only prevents name collisions but also allows for abstractions. There are three main features of the new module system:

1. Scopes, which allow name collisions to be avoided
2. Macros, which allow for abstraction and code reuse
3. Groups, which allow for code to be published as a library

Scopes

Scopes are a way to avoid name collisions as well as to structure code. These allow us to namespace our code. As a preliminary, there is a command that is essientally neccassary for scopes, that being %{ ... %}

Sequences

The command %{ ... %} allows us to turn mutiple commands into just one. The syntax for it is a little special, due to the fact that:

1. Commands which normally can only appear in the top level can now appear inside of it
2. It can be nested

These are handled as follows¹: There are two seperate commands, %{ and %}, the first one, %{, stops parsing the input and then restarts the parsing as if at the top of a file. If at any point the parser encounters a %}, it proceeds to stop parsing. If this happens without %{, this is an error. Otherwise, the %{ finally returns as a single command containing the entierity of the input parsed seperately. Parsing then continues as normal after the %}, using any state changes inside %{ ... %} as appropriate. This can be nested, with the nested calls going onto a stack.

Inserting Scopes

%scope %open %require

Macros

%macro NUM name CMD %0, %1 etc

Using

%use NAME (ARGS...)

Shorthands

%data NAME SORT_ARGS... %where ... -> %sort NAME SORT_ARGS... %. %scope NAME ...

Footnotes

1. The parsing dosen’t actually work like this, but its easier to understand it this way ↩