nl_tokens: The following functions cannot be made efficient on sparse arrays while preserving the semantics since the calls to the receiver function can add or delete elements from the array .
pl_tokens: function InnerArrayFilter ( f , receiver , <mask> , length , result ) { var result_length = 0 ; for ( var i = 0 ; i < length ; i ++ ) { if ( i in array ) { var element = array [ i ] ; if ( % _Call ( f , receiver , element , i , array ) ) { % CreateDataProperty ( result , result_length , element ) ; result_length ++ ; } } } return result ; }