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Include tagged data in simple category
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Part of #1132
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@jclark
jclark committed Oct 8, 2022
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Expand Up @@ -349,18 +349,16 @@ <h4>Type system fundamentals</h4>
</p>
<ul>
<li>simple values, like booleans and floating point numbers, which are not
constructed from other values;</li>
composed from other values;</li>
<li>structured values, like mappings and lists, which contain values of arbitrary basic types;</li>
<li>sequence values, which consists of sequences of values of the same basic type;</li>
<li>tagged data values, used for well-known data types with their own
specialized string syntax;</li>
<li>behavioral values, like functions and objects, which are not just data.</li>
</ul>
<p>
There is a fundamental distinction between values that have a <em>storage
identity</em> and values that do not. A value that has storage identity has an
identity that comes from the location where the value is stored. All structural
and behavioural values have a storage identity, whereas all simple values and tagged data values
and behavioural values have a storage identity, whereas all simple values
do not. Storage identity for sequence values is more complicated and will be
explained in the section on sequence values.
</p>
Expand Down Expand Up @@ -399,15 +397,13 @@ <h4>Type system fundamentals</h4>
mathematical value being represented.
</p>
<p>
A value is <em>plain data</em> if it is a simple value, a sequence value,
a tagged data value or a
A value is <em>plain data</em> if it is a simple value, a sequence value, or a
structured value that does not contain a behavioral value at any depth.
More precisely, a value is defined to be <em>plain data</em> if it is
</p>
<ul>
<li>a simple value,</li>
<li>a sequence value,</li>
<li>a tagged data value, or</li>
<li>a structured value, all of whose members are also plain data.</li>
</ul>
<p>
Expand Down Expand Up @@ -748,7 +744,6 @@ <h4>Type descriptors</h4>
simple-type-descriptor
| sequence-type-descriptor
| structured-type-descriptor
| tagged-data-type-descriptor
| behavioral-type-descriptor
| other-type-descriptor
</pre>
Expand Down Expand Up @@ -930,7 +925,7 @@ <h4>Iterability</h4>
<section>
<h3>Simple values</h3>
<p>
A simple value belongs to exactly one of the following basic types:
The basic type of a simple value is either one of the following
</p>
<ul>
<li>nil</li>
Expand All @@ -940,8 +935,7 @@ <h3>Simple values</h3>
<li>decimal</li>
</ul>
<p>
The type descriptor for each simple basic type contains all the values of the
basic type.
or is a tagged data type.
</p>
<p>
All simple basic types are inherently immutable.
Expand All @@ -953,7 +947,12 @@ <h3>Simple values</h3>
| boolean-type-descriptor
| int-type-descriptor
| floating-point-type-descriptor
| tagged-data-type-descriptor
</pre>
<p>
The type descriptor for each simple basic type contains all the values of the
basic type.
</p>
<section>
<h4>Nil</h4>

Expand Down Expand Up @@ -1112,6 +1111,67 @@ <h5>Decimal</h5>
</p>
</section>
</section>
<section>
<h4>Tagged data values</h4>

<p>
Tagged data types are used for well-known data types that are not
application-specific, but are widely supported across multiple protocols and
programming languages. Each of these data types has its own conventional string
syntax. The use of tagged data types allows programs to work with these data
types using their normal string syntax, while distinguishing the values as
belonging to a specific tagged data type.
</p>
<p>
Data tags are defined either by this specification or the Ballerina platform.
For each such data tag, there is a corresponding basic type. The definition of a
data tag specifies the set of values belonging to the corresponding basic type.
A tagged data value is a value belonging to one of these basic types. Every
tagged data value is plain data, immutable and has no storage identity. The
shape of a tagged data value is the value.
</p>
<p>
The definition of a data tag with corresponding basic type B specifies:
</p>
<ul>
<li>the name of the data tag; this is an unqualified identifier that is used
with the tagged-data-template-expr to construct a value of type B;</li>
<li>the set of values that B consists of;</li>
<li>an abstract parsing function, used at compile-time; a sequence of characters
into which <var>n</var> values can be interpolated is represented by an array of
<var>n</var> + 1 strings; the abstract parsing function accordingly takes an
array of <var>n</var> + 1 strings, with <var>n</var> &#x2065; 0, and returns
either an error or a function of <var>n</var> arguments that interpolates its
arguments into the result of the parse; the type of both the arguments and the
return value of the returned function is B;</li>
<li>an abstract function mapping from values of type B to strings;</li>
<li>a library module; method call expressions on values of type B will call
functions in this module.</li>
</ul>
<p>
Note that errors cannot happen during interpolation. The abstract parsing
function must therefore allow interpolations only in places where any valid
value of type B can be interpolated.
</p>
<p>
Most of the functionality of a tagged data type is provided by its library
module.
</p>

<pre
class="grammar">tagged-data-type-descriptor := qualified-identifier
</pre>
<p>
The qualified-identifier in a tagged-data-type-descriptor refers to a type that
is defined in a module that is part of the language library or standard library.
</p>
<p>
In this version of the Ballerina language, only the data tag <code>re</code>
is defined, with associated lang library module <code>lang.regexp</code>.
</p>

</section>

</section>
<section>
<h3>Sequence values</h3>
Expand Down Expand Up @@ -1869,66 +1929,6 @@ <h4 id="tables">Tables</h4>
</p>

</section>
</section>
<section>
<h3>Tagged data values</h3>

<p>
Tagged data types are used for well-known data types that are not
application-specific, but are widely supported across multiple protocols and
programming languages. Each of these data types has its own conventional string
syntax. The use of tagged data types allows programs to work with these data
types using their normal string syntax, while distinguishing the values as
belonging to a specific tagged data type.
</p>
<p>
Data tags are defined either by this specification or the Ballerina platform.
For each such data tag, there is a corresponding basic type. The definition of a
data tag specifies the set of values belonging to the corresponding basic type.
A tagged data value is a value belonging to one of these basic types. Every
tagged data value is plain data, immutable and has no storage identity. It is
also atomic, in the sense that it contains no references to other values.
</p>
<p>
The definition of a data tag with corresponding basic type B specifies:
</p>
<ul>
<li>the name of the data tag; this is an unqualified identifier that is used
with the tagged-data-template-expr to construct a value of type B;</li>
<li>the set of values that B consists of;</li>
<li>an abstract parsing function, used at compile-time; a sequence of characters
into which <var>n</var> values can be interpolated is represented by an array of
<var>n</var> + 1 strings; the abstract parsing function accordingly takes an
array of <var>n</var> + 1 strings, with <var>n</var> &#x2065; 0, and returns
either an error or a function of <var>n</var> arguments that interpolates its
arguments into the result of the parse; the type of both the arguments and the
return value of the returned function is B;</li>
<li>an abstract function mapping from values of type B to strings;</li>
<li>a library module; method call expressions on values of type B will call
functions in this module.</li>
</ul>
<p>
Note that errors cannot happen during interpolation. The abstract parsing
function must therefore allow interpolations only in places where any valid
value of type B can be interpolated.
</p>
<p>
Most of the functionality of a tagged data type is provided by its library
module.
</p>

<pre
class="grammar">tagged-data-type-descriptor := qualified-identifier
</pre>
<p>
The qualified-identifier in a tagged-data-type-descriptor refers to a type that
is defined in a module that is part of the language library or standard library.
</p>
<p>
In this version of the Ballerina language, only the data tag <code>re</code>
is defined, with associated lang library module <code>lang.regexp</code>.
</p>

</section>
<section>
<h3>Behavioral values</h3>
Expand Down

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