Hash#keep_if
, but returns ;TI".nil
if no changes were made.;T:
@fileI"hash.c;T:0@omit_headings_from_table_of_contents_below0I"nhsh.select! {| key, value | block } -> hsh or nil
hsh.select! -> an_enumerator
;T0[ I"();T@FI" Hash;TcRDoc::NormalClass00