frequency:deallocate(F) creates duplicates and inserts non-allocatable frequencies

[lbolla]

frequency:deallocate does not care what the allocatable frequencies are and happily inserts non-allocatable frequencies in the "allocatable" list, even duplicating them.

Erlang/OTP 18 [erts-7.3] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]

Eshell V7.3  (abort with ^G)
1> c(frequency).
frequency.erl:4: Warning: undefined callback function code_change/3 (behaviour 'gen_server')
{ok,frequency}
2> frequency:start().
{ok,<0.41.0>}
3> l(sys).
{module,sys}
4> sys:statistics(frequency, true).
ok
5> sys:get_state(frequency).
{[10,11,12,13,14,15],[]}
6> frequency:deallocate(999).
ok
7> sys:get_state(frequency). 
{[999,10,11,12,13,14,15],[]}
8> frequency:deallocate(10). 
ok
9> sys:get_state(frequency).
{[10,999,10,11,12,13,14,15],[]}