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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 /lib/compiler/test/map_SUITE.erl
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 'lib/compiler/test/map_SUITE.erl')
-rw-r--r--lib/compiler/test/map_SUITE.erl18
1 files changed, 18 insertions, 0 deletions
diff --git a/lib/compiler/test/map_SUITE.erl b/lib/compiler/test/map_SUITE.erl
index e98c295da6..6badc7a8b8 100644
--- a/lib/compiler/test/map_SUITE.erl
+++ b/lib/compiler/test/map_SUITE.erl
@@ -1203,12 +1203,18 @@ t_guard_bifs(Config) when is_list(Config) ->
true = map_guard_empty_2(),
true = map_guard_head(#{a=>1}),
false = map_guard_head([]),
+ true = map_get_head(#{a=>1}),
+ false = map_get_head([]),
+ true = map_is_key_head(#{a=>1}),
+ false = map_is_key_head(#{}),
true = map_guard_body(#{a=>1}),
false = map_guard_body({}),
true = map_guard_pattern(#{a=>1, <<"hi">> => "hi" }),
false = map_guard_pattern("list"),
true = map_guard_tautology(),
true = map_guard_ill_map_size(),
+ true = map_field_check_sequence(#{a=>1}),
+ false = map_field_check_sequence(#{}),
ok.
map_guard_empty() when is_map(#{}); false -> true.
@@ -1218,6 +1224,12 @@ map_guard_empty_2() when true; #{} andalso false -> true.
map_guard_head(M) when is_map(M) -> true;
map_guard_head(_) -> false.
+map_get_head(M) when map_get(a, M) =:= 1 -> true;
+map_get_head(_) -> false.
+
+map_is_key_head(M) when is_map_key(a, M) -> true;
+map_is_key_head(M) -> false.
+
map_guard_body(M) -> is_map(M).
map_guard_pattern(#{}) -> true;
@@ -1227,6 +1239,12 @@ map_guard_tautology() when #{} =:= #{}; true -> true.
map_guard_ill_map_size() when true; map_size(0) -> true.
+map_field_check_sequence(M)
+ when is_map(M) andalso is_map_key(a, M) andalso (map_get(a, M) == 1) ->
+ true;
+map_field_check_sequence(_) ->
+ false.
+
t_guard_sequence(Config) when is_list(Config) ->
{1, "a"} = map_guard_sequence_1(#{seq=>1,val=>id("a")}),
{2, "b"} = map_guard_sequence_1(#{seq=>2,val=>id("b")}),