Function expressions

[matthew-mojira]

Function values allow for anonymous functions and declared name functions.

Also, cool features that would be useful (some stolen from Dafny):

• preconditions
• postconditions
• invariants? (only in loops?)
• integrated unit tests

[matthew-mojira]

forbid duplicate parameter names in the parser

[matthew-mojira]

10

[matthew-mojira]

anonymous functions are not closures over the environment in which they are written. Should they be?

[matthew-mojira]

From #8: box and unbox should have its implementation provided by the interpreter