The function binders returns a list of all the binders declared so far. A
binder b is then parsed in constructs like b x. t[x] as an abbreviation for
(b) (\x. t[x]). The set of binders can be changed with parse_as_binder and
unparse_as_binder.
FAILURE CONDITIONS
Never fails
EXAMPLE
# binders();;
val it : string list = ["\\"; "!"; "?"; "?!"; "@"; "minimal"; "lambda"]