Define the look-up process for oFrugal binding resolution

[orcmid]

There needs to be a function for

1. Inserting the bound ob for a binding name into a binding data structure (a list)

2. Checking to see if a binding name has a bound ob and returning that, returning a ?-prefixed lindy when there is no bound ob for that name.

The data structure is passed forward into subsequent oFrugal statements, so that all syntactically-valid oFrugal REPL always have a successful interpretation.

[orcmid]

The basic function is this, there may be different lists, such as one for primitives and one for plain lindies.

The entries in the list are pairs where the b-path is the text of a string and the a-path is the value. The list of entries bottoms out on a singleton, usually NIL.

We draw the lists as [value::string, value::string, ..., value::string] and we assume a string-equality check.

The basic search is

let binding(s, List) 
     = if is-singleton(List)
         then mklindy( prefix("?", s) )
         else if .b .a List = s)
                then .a .a List
                else binding(s, .b List);

the insertion of a binding onto the list is

let update(List, s, ob)
     = (ob :: s) :: List;

there is no removal process. The most-recent for given s is the one that will be found.