A Bounded_int_table
is a table whose keys can be mapped to integers in a fixed
range, 0 ... num_keys-1, where num_keys
is specified at table-creation time. The
purpose of Bounded_int_table
is to be faster than Hashtbl
in situations where one
is willing to pay a space cost for the speed.
Bounded_int_table
presents a subset of the Hashtbl
interface. The key type can be
any type, but table creation requires a key_to_int
function, which will be used
to extract the integer of all keys. If multiple keys map to the same integer, then
only one of them can be in the table at a time. Any operation that supplies a key
whose corresponding integer is outside the allowed range for the table will cause an
exception.
A Bounded_int_table
is implemented using two fixed size arrays of size num_keys
,
which are supplied at table-creation time. The space used does not depend on the
length
of the table but rather only on num_keys
. Operations that deal with a
single element (find, mem, add, remove, set) take constant time, and perform one or
two array operations. Operations that deal with all of the keys defined in the table
(data, fold, iter, iter_vals, keys, to_alist) take time proportional to the length
of the table, not num_keys
.
create ~num_keys ~key_to_int
returns a table where the keys can map to 0
.. num_keys-1, according to key_to_int
. It is an error if num_keys < 0
.
sexp_of_key
, if supplied, will be used to display keys in error messages.
Standard hashtbl functions.
set debug := true
to turn on debugging, including potentially slow invariant
checking.