thought.txt

add ctx to toString -- This is hard because you need a context for each symbol
and variable type the thing can depend on. Also this would add a dependency on
contexts to the generated code, but maybe having Var.Dict is a good idea anyway.

Respect user's choice of order as much as possible.

Add all (or just more) sml primitive types as builtins
(unit, int, word, real, char, string, substring, vector, bool, option, order).

Define what it means for an abt spec to be well-formed, and make parser/analysis
check that, then fix internal names:

check that things are applied to the right number of arguments

names must start with a letter and may include letters, numbers, and _
this means any sml name, except that ' is disallowed

??? allow symbol names like ">>" ???
??? allow infix operators ???

Reserved words:
Abbot
sort
abt, Abt
symbol, Symbol
list
view
into
out
aequiv
map
subst ^ anything
iter ??? might not be necessary to restrict this
all sml reserved words and restricted identifiers

all opers in the same sort or abt must be unique, but the same oper can be
duplicated across asts and abts

sorts and abts may refer to sorts, abts, and symbols

symbol, abt, and sort names must be unique and mutually exclusive, up to
capitalization

abt applications must use the correct aritys

type parameters used in abt declaration must be in the arguments of that ast

okay names include: var, variable, sym, t, temp, exp_oper,

names can be concatenation of other names

??? restrict use of Ops or something ???
??? what happens when names end in numbers ???

convention for variable names: internal names end in "'", names generated from
the user's names are the user's name followed by "'", followed by a number