From 5d0874a8f9fd617308d9024783db1e4e24268184 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micha=C5=82=20Muska=C5=82a?= Date: Fri, 27 Apr 2018 12:40:07 +0200 Subject: 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. --- erts/doc/src/erlang.xml | 20 +++++++++++++++ erts/doc/src/match_spec.xml | 23 +++++++++--------- erts/emulator/beam/bif.tab | 1 + erts/emulator/beam/erl_db_util.c | 6 +++++ erts/emulator/beam/erl_map.c | 7 +++++- erts/emulator/test/map_SUITE.erl | 43 ++++++++++++++++++++++++++++++++- erts/emulator/test/match_spec_SUITE.erl | 7 ++++++ erts/preloaded/src/erlang.erl | 9 ++++++- 8 files changed, 102 insertions(+), 14 deletions(-) (limited to 'erts') diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index f561413fab..3154fdaf8c 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -2431,6 +2431,26 @@ os_prompt% + + + + +

Returns true if map Map contains + Key and returns false if it does not + contain the Key.

+

The call fails with a {badmap,Map} exception if + Map is not a map.

+

Example:

+ +> Map = #{"42" => value}. +#{"42" => value} +> is_map_key("42",Map). +true +> is_map_key(value,Map). +false + + + Check whether a term is a number. diff --git a/erts/doc/src/match_spec.xml b/erts/doc/src/match_spec.xml index 888366b239..46a3daebe8 100644 --- a/erts/doc/src/match_spec.xml +++ b/erts/doc/src/match_spec.xml @@ -86,12 +86,12 @@ | | | | | | - | | - | | - | | - | | - | | - + | | + | | + | | + | | + | | + | ConditionExpression ::= ExprMatchVariable | { GuardFunction } | { GuardFunction, ConditionExpression, ... } | TermConstruct @@ -168,11 +168,12 @@ | | | | | | - | | - | | - | | - | | - | + | | + | | + | | + | | + | | + ConditionExpression ::= ExprMatchVariable | { GuardFunction } | { GuardFunction, ConditionExpression, ... } | TermConstruct diff --git a/erts/emulator/beam/bif.tab b/erts/emulator/beam/bif.tab index 276bef2bbb..33738dc20b 100644 --- a/erts/emulator/beam/bif.tab +++ b/erts/emulator/beam/bif.tab @@ -696,3 +696,4 @@ bif ets:whereis/1 bif erts_internal:gather_alloc_histograms/1 bif erts_internal:gather_carrier_info/1 ubif erlang:map_get/2 +ubif erlang:is_map_key/2 diff --git a/erts/emulator/beam/erl_db_util.c b/erts/emulator/beam/erl_db_util.c index 6354abfd1f..ef22cda1f0 100644 --- a/erts/emulator/beam/erl_db_util.c +++ b/erts/emulator/beam/erl_db_util.c @@ -643,6 +643,12 @@ static DMCGuardBif guard_tab[] = 2, DBIF_ALL }, + { + am_is_map_key, + &is_map_key_2, + 2, + DBIF_ALL + }, { am_bit_size, &bit_size_1, diff --git a/erts/emulator/beam/erl_map.c b/erts/emulator/beam/erl_map.c index f577b017c3..3d565b1bb8 100644 --- a/erts/emulator/beam/erl_map.c +++ b/erts/emulator/beam/erl_map.c @@ -43,6 +43,7 @@ * * DONE: * - erlang:is_map/1 + * - erlang:is_map_key/2 * - erlang:map_size/1 * - erlang:map_get/2 * @@ -919,7 +920,7 @@ static int hxnodecmp(hxnode_t *a, hxnode_t *b) { return -1; } -/* maps:is_key/2 */ +/* maps:is_key/2 and erlang:is_map_key/2 */ BIF_RETTYPE maps_is_key_2(BIF_ALIST_2) { if (is_map(BIF_ARG_2)) { @@ -929,6 +930,10 @@ BIF_RETTYPE maps_is_key_2(BIF_ALIST_2) { BIF_ERROR(BIF_P, BADMAP); } +BIF_RETTYPE is_map_key_2(BIF_ALIST_2) { + BIF_RET(maps_is_key_2(BIF_CALL_ARGS)); +} + /* maps:keys/1 */ BIF_RETTYPE maps_keys_1(BIF_ALIST_1) { 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 <- lists:seq(1,415)], diff --git a/erts/preloaded/src/erlang.erl b/erts/preloaded/src/erlang.erl index 53e90a4f2d..5fcad25c6d 100644 --- a/erts/preloaded/src/erlang.erl +++ b/erts/preloaded/src/erlang.erl @@ -135,7 +135,7 @@ -export([insert_element/3]). -export([integer_to_binary/1, integer_to_list/1]). -export([iolist_size/1, iolist_to_binary/1, iolist_to_iovec/1]). --export([is_alive/0, is_builtin/3, is_process_alive/1, length/1, link/1]). +-export([is_alive/0, is_builtin/3, is_map_key/2, is_process_alive/1, length/1, link/1]). -export([list_to_atom/1, list_to_binary/1]). -export([list_to_bitstring/1, list_to_existing_atom/1, list_to_float/1]). -export([list_to_integer/1, list_to_integer/2]). @@ -1121,6 +1121,13 @@ is_alive() -> is_builtin(_Module, _Function, _Arity) -> erlang:nif_error(undefined). +%% Shadowed by erl_bif_types: erlang:is_map_key/2 +-spec is_map_key(Key, Map) -> boolean() when + Key :: term(), + Map :: map(). +is_map_key(_,_) -> + erlang:nif_error(undef). + %% is_process_alive/1 -spec is_process_alive(Pid) -> boolean() when Pid :: pid(). -- cgit v1.2.3