CODING CONVENTIONS

* naming conventions

type names:        FOO_BAR
constructor names: FooBar
local/field names: fooBar

* non-exhaustive matches

During implementation, non-exhaustive match warnings are fine (they
help us keep track of what hasn't been implemented). But completed
code should not have non-exhaustive matches.

If a particular case should never happen, the right-hand side of the
match case should raise a Fail exception with a string indicating what
invariant was violated.

* explicit type annotations

Top-level functions must be annotated explicitly.

* line widths

Lines must not exceed 100 columns.

* indentation

[TODO]

* tabs

Hard tabs are disallowed.