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| author | Magnus Henoch <[email protected]> | 2013-09-04 14:08:34 +0100 |
|---|---|---|
| committer | Magnus Henoch <[email protected]> | 2013-09-13 10:44:23 +0100 |
| commit | 0e4b0ae7ce57117a561f70fa51026d85b4702aaa (patch) | |
| tree | 4a0aba55aaeef71d6f2abed3b8aec50cd0018c6a /lib/stdlib/src | |
| parent | 5b56a49d15d10ad4a35dbc8b2a4b01486f1d5294 (diff) | |
| download | otp-0e4b0ae7ce57117a561f70fa51026d85b4702aaa.tar.gz otp-0e4b0ae7ce57117a561f70fa51026d85b4702aaa.tar.bz2 otp-0e4b0ae7ce57117a561f70fa51026d85b4702aaa.zip | |
Add dict:is_empty/1 and orddict:is_empty/1
dict:size/1 runs in constant time, but orddict:size/1 does not. With
this change, the two modules stay API compatible and gain a
constant-time function for checking whether a dictionary is empty.
Diffstat (limited to 'lib/stdlib/src')
| -rw-r--r-- | lib/stdlib/src/dict.erl | 7 | ||||
| -rw-r--r-- | lib/stdlib/src/orddict.erl | 8 |
2 files changed, 13 insertions, 2 deletions
diff --git a/lib/stdlib/src/dict.erl b/lib/stdlib/src/dict.erl index e3bfb6c2e2..e67433ffb7 100644 --- a/lib/stdlib/src/dict.erl +++ b/lib/stdlib/src/dict.erl @@ -36,7 +36,7 @@ -module(dict). %% Standard interface. --export([new/0,is_key/2,to_list/1,from_list/1,size/1]). +-export([new/0,is_key/2,to_list/1,from_list/1,size/1,is_empty/1]). -export([fetch/2,find/2,fetch_keys/1,erase/2]). -export([store/3,append/3,append_list/3,update/3,update/4,update_counter/3]). -export([fold/3,map/2,filter/2,merge/3]). @@ -112,6 +112,11 @@ from_list(L) -> size(#dict{size=N}) when is_integer(N), N >= 0 -> N. +-spec is_empty(Dict) -> boolean() when + Dict :: dict(). + +is_empty(#dict{size=N}) -> N =:= 0. + -spec fetch(Key, Dict) -> Value when Key :: term(), Dict :: dict(), diff --git a/lib/stdlib/src/orddict.erl b/lib/stdlib/src/orddict.erl index 45d3c84b3e..da60fc1bb6 100644 --- a/lib/stdlib/src/orddict.erl +++ b/lib/stdlib/src/orddict.erl @@ -20,7 +20,7 @@ -module(orddict). %% Standard interface. --export([new/0,is_key/2,to_list/1,from_list/1,size/1]). +-export([new/0,is_key/2,to_list/1,from_list/1,size/1,is_empty/1]). -export([fetch/2,find/2,fetch_keys/1,erase/2]). -export([store/3,append/3,append_list/3,update/3,update/4,update_counter/3]). -export([fold/3,map/2,filter/2,merge/3]). @@ -64,6 +64,12 @@ from_list(Pairs) -> size(D) -> length(D). +-spec is_empty(Orddict) -> boolean() when + Orddict :: orddict(). + +is_empty([]) -> true; +is_empty([_|_]) -> false. + -spec fetch(Key, Orddict) -> Value when Key :: term(), Value :: term(), |