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authorMichał Muskała <[email protected]>2018-04-27 12:40:07 +0200
committerMichał Muskała <[email protected]>2018-04-29 17:03:43 +0200
commit5d0874a8f9fd617308d9024783db1e4e24268184 (patch)
treeac61f2f0f8d7f7483af9e17df44b49aeb049e695 /erts/emulator/test
parentd423a7af502227afcdcf7d2a1efecded85ea95fb (diff)
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Introduce is_map_key/2 guard BIF
This complements the `map_get/2` guard BIF introduced in #1784. Rationale. `map_get/2` allows accessing map fields in guards, but it might be problematic in more complex guard expressions, for example: foo(X) when map_get(a, X) =:= 1 or is_list(X) -> ... The `is_list/1` part of the guard could never succeed since the `map_get/2` guard would fail the whole guard expression. In this situation, this could be solved by using `;` instead of `or` to separate the guards, but it is not possible in every case. To solve this situation, this PR proposes a `is_map_key/2` guard that allows to check if a map has key inside a guard before trying to access that key. When combined with `is_map/1` this allows to construct a purely boolean guard expression testing a value of a key in a map. Implementation. Given the use case motivating the introduction of this function, the PR contains compiler optimisations that produce optimial code for the following guard expression: foo(X) when is_map(X) and is_map_key(a, X) and map_get(a, X) =:= 1 -> ok; foo(_) -> error. Given all three tests share the failure label, the `is_map_key/2` and `is_map/2` tests are optimised away. As with `map_get/2` the `is_map_key/2` BIF is allowed in match specs.
Diffstat (limited to 'erts/emulator/test')
-rw-r--r--erts/emulator/test/map_SUITE.erl43
-rw-r--r--erts/emulator/test/match_spec_SUITE.erl7
2 files changed, 49 insertions, 1 deletions
diff --git a/erts/emulator/test/map_SUITE.erl b/erts/emulator/test/map_SUITE.erl
index 43807b4388..f93c637650 100644
--- a/erts/emulator/test/map_SUITE.erl
+++ b/erts/emulator/test/map_SUITE.erl
@@ -38,6 +38,7 @@
t_map_size/1,
t_map_get/1,
t_is_map/1,
+ t_is_map_key/1,
%% Specific Map BIFs
t_bif_map_get/1,
@@ -718,7 +719,47 @@ t_map_get(Config) when is_list(Config) ->
true = if map_get(a, M2) =:= 1 -> true; true -> false end,
false = if map_get(x, M2) =:= 1 -> true; true -> false end,
do_badmap(fun
- (T) when map_get(T, x) =:= 1 -> ok;
+ (T) when map_get(x, T) =:= 1 -> ok;
+ (T) -> false = is_map(T)
+ end),
+ ok.
+
+t_is_map_key(Config) when is_list(Config) ->
+ %% small map
+ true = is_map_key(a, id(#{a=>1})),
+ true = is_map_key(b, id(#{a=>1, b=>2})),
+ true = is_map_key("hello", id(#{a=>1, "hello"=>"hi"})),
+ true = is_map_key({1,1.0}, id(#{a=>a, {1,1.0}=>"tuple hi"})),
+
+ M0 = id(#{ k1=>"v1", <<"k2">> => <<"v3">> }),
+ true = is_map_key(<<"k2">>, M0#{<<"k2">> => "v4"}),
+
+ %% large map
+ M1 = maps:from_list([{I,I}||I<-lists:seq(1,100)] ++
+ [{a,1},{b,2},{"hello","hi"},{{1,1.0},"tuple hi"},
+ {k1,"v1"},{<<"k2">>,"v3"}]),
+ true = is_map_key(a, M1),
+ true = is_map_key(b, M1),
+ true = is_map_key("hello", M1),
+ true = is_map_key({1,1.0}, M1),
+ true = is_map_key(<<"k2">>, M1),
+
+ %% error cases
+ do_badmap(fun(T) ->
+ {'EXIT',{{badmap,T},[{erlang,is_map_key,_,_}|_]}} =
+ (catch is_map_key(a, T))
+ end),
+
+ false = is_map_key({1,1}, id(#{{1,1.0}=>"tuple"})),
+ false = is_map_key(a, id(#{})),
+ false = is_map_key(a, id(#{b=>1, c=>2})),
+
+ %% in guards
+ M2 = id(#{a=>1}),
+ true = if is_map_key(a, M2) -> true; true -> false end,
+ false = if is_map_key(x, M2) -> true; true -> false end,
+ do_badmap(fun
+ (T) when is_map_key(T, x) =:= 1 -> ok;
(T) -> false = is_map(T)
end),
ok.
diff --git a/erts/emulator/test/match_spec_SUITE.erl b/erts/emulator/test/match_spec_SUITE.erl
index c1bc01f01e..4415d8d1b9 100644
--- a/erts/emulator/test/match_spec_SUITE.erl
+++ b/erts/emulator/test/match_spec_SUITE.erl
@@ -898,6 +898,13 @@ maps(Config) when is_list(Config) ->
{ok,false,[],[]} = erlang:match_spec_test(not_a_map, [{'$1',[{map_get,b,'$1'}],['$_']}], table),
{ok,true,[],[]} = erlang:match_spec_test(#{a => true}, [{'$1',[{map_get,a,'$1'}],[true]}], table),
+ {ok,true,[],[]} = erlang:match_spec_test(#{a => 1}, [{'$1',[],[{is_map_key,a,'$1'}]}], table),
+ {ok,false,[],[]} = erlang:match_spec_test(#{a => 1}, [{'$1',[],[{is_map_key,b,'$1'}]}], table),
+ {ok,'EXIT',[],[]} = erlang:match_spec_test(not_a_map, [{'$1',[],[{is_map_key,a,'$1'}]}], table),
+ {ok,false,[],[]} = erlang:match_spec_test(#{a => 1}, [{'$1',[{is_map_key,b,'$1'}],['$_']}], table),
+ {ok,false,[],[]} = erlang:match_spec_test(not_a_map, [{'$1',[{is_map_key,b,'$1'}],['$_']}], table),
+ {ok,true,[],[]} = erlang:match_spec_test(#{a => true}, [{'$1',[{is_map_key,a,'$1'}],[true]}], table),
+
%% large maps
Ls0 = [{I,<<I:32>>}||I <- lists:seq(1,415)],