Language specification

[Idorobots]

At this point it would be a pretty good idea to define what this language actually supports and how it looks.

[Idorobots]

Should defs be allowed at any position? Should these evaluate to the value? Should these be lifted into the closest enclosing scope?

[Idorobots]

Related: #120 #121
Also #91 #145

[Idorobots]

Should booleans have dedicated values or should we just wing it and use nil. She'll be 'aight.

[Idorobots]

Consider non-sexp syntax? https://github.com/mflatt/rhombus-prototype/blob/shrubbery/shrubbery/0000-shrubbery.md

[Idorobots]

Consider the following:

• Dedicated boolean values for "true" & "false" (as opposed to anything and "nil" currently) simplify the implementation of primops in different languages.
• Better pattern matching can be used to not to have to have boolean values in the first place.
• Disallow improper lists. Given that arrays arewill be available as basic building blocks with low overhead (and at that support more than two slots) this should only simplify generating code for languages with a notion of collections.
• Disallow vararg functions. With arrays self-evaluating it shouldn't be too inconvenient. Given pattern matching it should actually be pretty OK. ™️