nomsu/core/id.nom

#!/usr/bin/env nomsu -V6.14
#
    A simple UUID function based on RFC 4122: http://www.ietf.org/rfc/rfc4122.txt
    
use "core/metaprogramming.nom"
use "core/operators.nom"
use "core/math.nom"
use "core/collections.nom"
use "core/control_flow.nom"

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

$NaN_surrogate = {}
$nil_surrogate = {}
$obj_by_id = {}
set $obj_by_id's metatable to {.__mode = "v"}
$id_by_obj = {}
set $id_by_obj's metatable to {
    .__mode = "k"
    .__index =
        for ($self $key):
            if ($key == (nil)):
                return $self.$nil_surrogate
            
            if ($key != $key):
                return $self.$NaN_surrogate
            
            --- (retry) ---
            $id = (uuid)
            if ($obj_by_id.$id != (nil)): go to (retry)
            $self.$key = $id
            $obj_by_id.$id = $key
            return $id
}

externally (uuid) means:
    # Set all the other bits to randomly (or pseudo-randomly) chosen values.
    $bytes = [
        # time-low, time-mid, time-high-and-version
        randint (2 ^ (4 * 8)), randint (2 ^ (2 * 8)), randint (2 ^ (2 * 8 - 4))
        # clock-seq-and-reserved, clock-seq-low
        randint (2 ^ (1 * 8 - 2)), randint (2 ^ (1 * 8)), randint (2 ^ (3 * 8))
        # node
        randint (2 ^ (3 * 8))
    ]
    
    # Set the four most significant bits (bits 12 through 15) of the
    # time_hi_and_version field to the 4-bit version number from
    # Section 4.1.3.
    $bytes.3 += 0x4000
    
    # Set the two most significant bits (bits 6 and 7) of the
    # clock_seq_hi_and_reserved to zero and one, respectively.
    $bytes.4 += 0xC0
    return (=lua "('%08x-%04x-%04x-%02x%02x-%6x%6x'):format(unpack(\$bytes))")

# For strict identity checking, use ($x's id) == ($y's id)
test:
    assume (([] == []) and ((id of []) != (id of [])))
    seed random with 0
    $x = []
    assume ((id of $x) == (id of $x))
    seed random with 0
    assume ((id of $x) != (id of []))
    seed random
externally [id of $, $'s id, $'id] all mean $id_by_obj.$