Selector simplified pseudo code

def performSelector():
    worlds = sender world if has any of r/rm/x/y/z/dx/dy/dz else all worlds (overworld, nether and end order)
    list = []

    for world in worlds:
        registerPredicates()
        if @s:
            return @s if still match, nothing otherwise
        else:
            list += performPredicateMatching() #in world
    return getResult(list)



def registerPredicates():
    #all the predicate registry is pretty straight forward, but there is some special cases:

    if type= is unspecified, add a type=player predicate for @a and @p
    xp predicate only registered if at least one of l/lm is specified, and (l > -1 or lm > -1) default to -1 if unspecified
    xp/gamemode predicate only apply to EntityPlayerMP
    team predicate only apply to EntityLivingBase
    radius predicate only register if at least one of r/rm is specified, and (r >= -0.5 or rm >= 0.5) default to -1 if unspecified
    rx/rxm predicate only register if at least one of rx/rxm is specified, rx default to 0 and rxm default to 359
    same for ry/rym


#This method will apply the predicates in type/xp/gamemode/team/score/name/tag/radius/rotation order to all the entities it loop/scan and returns only the matching ones
def performPredicateMatching():
    if has dx/dy/dz:
        if @a @p (or @r with no type=):
            loop all alive players with a dx/dy/dz predicate (so no chunk scan)
        else:
            scan all alive entities in dx/dy/dz bounding Box

    else:
        if r >= 0 (when r is unspecified, r = -1):
            if @a @p (or @r with no type=):
                loop all alive players
            else:
                scan all alive entities in r= bounding Box
        else if @a:
            loop all players (here is the only case where dead players can be selected)
        else if @p (or @r with no type=):
            loop all alive players
        else:
            #it should only be @e and @r[type=] or @r[type=!]
            loop all entities


def getResult(list):
    if @r:
        shuffle list in O(n)
    else:
        distance sort list in O(n*log(n))

    #the c get his value from the specified argument, if c is unspecified, it will be 0 for @a/@e and 1 for @p/@r

    if sender in list and c==1 and not @r:
        return sender

    if c == 0:
        return list
    if c < 0:
        reverse list in O(n)

    truncate list by only keeping his c first elements
    return list