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-rw-r--r--system/doc/reference_manual/typespec.xml32
1 files changed, 23 insertions, 9 deletions
diff --git a/system/doc/reference_manual/typespec.xml b/system/doc/reference_manual/typespec.xml
index c5d24a96b5..9e26e9058d 100644
--- a/system/doc/reference_manual/typespec.xml
+++ b/system/doc/reference_manual/typespec.xml
@@ -132,15 +132,18 @@
| nonempty_list(Type) %% Proper non-empty list
Map :: map() %% stands for a map of any size
- | #{} %% stands for a map of any size
+ | #{} %% stands for the empty map
| #{PairList}
Tuple :: tuple() %% stands for a tuple of any size
| {}
| {TList}
- PairList :: Type => Type
- | Type => Type, PairList
+ PairList :: Pair
+ | Pair, PairList
+
+ Pair :: Type := Type %% notes a pair that must be present
+ | Type => Type
TList :: Type
| Type, TList
@@ -170,6 +173,23 @@
The notation <c>[]</c> specifies the singleton type for the empty list.
</p>
<p>
+ The general form of maps is <c>#{PairList}</c>. The key types in
+ <c>PairList</c> are allowed to overlap, and if they do, the leftmost pair
+ takes precedence. A map value does not belong to this type if contains a key
+ that is not in <c>PairList</c>.
+ </p>
+ <p>
+ Because it is common to end a map type with <c>any() =&gt; any()</c> to denote
+ that keys that do not belong to any other pair in <c>PairList</c> are
+ allowed, and may map to any value, the shorthand notation <c>...</c> is
+ allowed as the last pair of a map type.
+ </p>
+ <p>
+ Notice that the syntactic representation of <c>map()</c> is <c>#{...}</c>
+ (or <c>#{_ =&gt; _}</c>, or <c>#{any() =&gt; any()}</c>), not <c>#{}</c>.
+ The notation <c>#{}</c> specifies the singleton type for the empty map.
+ </p>
+ <p>
For convenience, the following types are also built-in.
They can be thought as predefined aliases for the type unions also shown in
the table.
@@ -302,12 +322,6 @@
This is described in <seealso marker="#typeinrecords">
Type Information in Record Declarations</seealso>.
</p>
- <note>
- <p>Map types, both <c>map()</c> and <c>#{...}</c>,
- are considered experimental during OTP 17.</p>
- <p>No type information of maps pairs, only the containing map types,
- are used by Dialyzer in OTP 17.</p>
- </note>
</section>
<section>