Document 'Init' data type with examples

docs/_openvox_8x/lang_data_abstract.md

@@ -13,16 +13,16 @@
 [hash_missing_key_access]: ./lang_data_hash.html#accessing-values
 [numbers]: ./lang_data_number.html
 
 As described in [the Data Type Syntax][types] page, each of Puppet's main [data types][] has a corresponding value that _represents_ that data type, which can be used to match values of that type in several contexts. (For example, `String` or `Array`.)
 
 Each of those core data types will only match a particular set of values. They let you further restrict the values they'll match, but only in limited ways, and there's no way to _expand_ the set of values they'll match.
 
 If you're using data types to match or restrict values and need more flexibility, you can use one of the _abstract data types_ on this page to construct a data type that suits your needs and matches the values you want.
 
 
 ## Flexible data types
 
 These abstract data types can match values with a variety of concrete data types. Some of them are similar to a concrete type but offer alternate ways to restrict them (like `Enum`), and some of them let you combine types and match a union of what they would individually match (like `Variant` and `Optional`).
 
 ### `Optional`
 
@@ -38,8 +38,8 @@
 
     Optional[<DATA TYPE>]
 
 Position | Parameter        | Data Type | Default Value | Description
 ---------| -----------------|-----------|---------------|------------
 1 | Data type | `Type` or `String` | none **(mandatory)** | The data type to add `undef` to.
 
 `Optional` also allows you to specify a string as its parameter, which is a shortcut for `Optional[Enum["my string"]]` --- it will match only that exact string value or `undef`.
@@ -282,7 +282,6 @@
 
 The `Any` data type matches _any_ value of _any_ data type.
 
-
 ## Unusual types
 
 These types aren't quite like the others.
@@ -308,3 +307,36 @@
 -2 | Max count | `Integer` | infinity | The maximum number of arguments the lambda accepts. This parameter accepts the special value `default`, which will use its default value.
 -1 | Block type | `Type[Callable]` | none | The `block_type` of the lambda.
 
+### `Init`
+
+The `Init` data type matches values that can be used as the initialization/typecase of another data type given as a parameter. This can be used to test if a value can be converted to the wanted data type.
+
+#### Parameters
+
+The signature for `Init` is:
+
+    Init[ <DATA TYPE> ]
+
+#### Examples
+
+Check if a string value can be converted to a `SemVer`:
+
+``` puppet
+"1.2.3" =~ Init[SemVer]    # result is true
+"latest" =~ Init[SemVer]   # result is false
+```
+
+Check if a value can be converted to an `Integer`:
+
+```
+"10" =~ Init[Integer]    # result is true
+"blue" =~ Init[Integer]  # result is false
+```
+
+Accept a parameter value that is either an `Integer` or a value convertible to one:
+
+``` puppet
+function example(Variant[Integer, Init[Integer]] $x) {
+   $int_value = Integer($x)  # Safe conversion
+}
+```