There's a bunch of informal types in folk, such as quads, spaces, libraries, etc. It would be useful to have a standard representation between different parts of the system, to aid in introspection and consistency.

Goals:

• Automatic visualization (á la Glamorous Toolkit)
• Type descriptions
• Automatic preconditions and verification
• Extensible (don't want to be locked in with a bad design)
• Flexible (this is tcl after all)

Non goals:

• Complex types
• Soundness
• One Unified Type System

Types will be tagged with their type name, and optionally with type parameters.

I'm not sure which way to go.

Pros of postfix:

• Types like “10 mm” are automatically a two item list, and as such are a full type

Cons of postfix:

• If the value is long, it will exceed the text boundaries, and as such the tag won't be rendered. (Somewhat mitigated by having something like `[typeof $foo]`)

Pros of prefix:

• A lot of current types are already in the prefix form

Cons of prefix:

• Makes constructing some types harder (like “10 mm”)