Merge pull request #1137 from michaelhkay/161-variadic-functions

161 Variadic functions

specifications/xpath-functions-40/src/fos.xsd

@@ -210,6 +210,7 @@
       <xs:enumeration value="context-independent"/>
       <xs:enumeration value="higher-order"/>
       <xs:enumeration value="special-streaming-rules"/>
+      <xs:enumeration value="variadic"/>
     </xs:restriction>
   </xs:simpleType>
   <xs:element name="summary">

specifications/xpath-functions-40/src/function-catalog.xml

@@ -3727,6 +3727,7 @@ translate(value := '٢٠٢٣', replace := '٠١٢٣٤٥٦٧٨٩', with := '01234
          <fos:property>deterministic</fos:property>
          <fos:property>context-independent</fos:property>
          <fos:property>focus-independent</fos:property>
+         <fos:property>variadic</fos:property>
       </fos:properties>
       <fos:summary>
          <p>Returns an <code>xs:string</code> whose characters have supplied <termref
@@ -3738,6 +3739,9 @@ translate(value := '٢٠٢٣', replace := '٠١٢٣٤٥٦٧٨٩', with := '01234
                >codepoints</termref> are
             supplied in <code>$values</code>. This will be the zero-length string if <code>$values</code>
             is the empty sequence. </p>
+         <p>In 4.0 the function is declared to be variadic, so the call 
+            <code>codepoints-to-string(66, 65, 67, 72)</code> is now equivalent to
+            <code>codepoints-to-string((66, 65, 67, 72))</code>.</p>
 
       </fos:rules>
       <fos:errors>
@@ -3753,7 +3757,15 @@ translate(value := '٢٠٢٣', replace := '٠١٢٣٤٥٦٧٨٩', with := '01234
                <fos:result>"BACH"</fos:result>
             </fos:test>
             <fos:test>
-               <fos:expression>codepoints-to-string((2309, 2358, 2378, 2325))</fos:expression>
+               <fos:expression>codepoints-to-string(66, 65, 67, 72)</fos:expression>
+               <fos:result>"BACH"</fos:result>
+            </fos:test>
+            <fos:test>
+               <fos:expression>codepoints-to-string((66, 65), (67, 72))</fos:expression>
+               <fos:result>"BACH"</fos:result>
+            </fos:test>
+            <fos:test>
+               <fos:expression>codepoints-to-string(2309, 2358, 2378, 2325)</fos:expression>
                <fos:result>"अशॊक"</fos:result>
             </fos:test>
             <fos:test>
@@ -4131,7 +4143,7 @@ translate(value := '٢٠٢٣', replace := '٠١٢٣٤٥٦٧٨٩', with := '01234
    <fos:function name="concat" prefix="fn">
       <fos:signatures>
          <fos:proto name="concat" return-type="xs:string">
-            <fos:arg name="..." type="xs:anyAtomicType*"/>
+            <fos:arg name="values" type="xs:anyAtomicType*" default="()"/>
          </fos:proto>
       </fos:signatures>
       <fos:opermap operator="||" types="xs:anyAtomicType xs:anyAtomicType"
@@ -4141,30 +4153,29 @@ translate(value := '٢٠٢٣', replace := '٠١٢٣٤٥٦٧٨٩', with := '01234
          <fos:property>deterministic</fos:property>
          <fos:property>context-independent</fos:property>
          <fos:property>focus-independent</fos:property>
+         <fos:property>variadic</fos:property>
       </fos:properties>
       <fos:summary>
          <p>Returns the concatenation of the string values of the arguments.</p>
       </fos:summary>
       <fos:rules>
-         <p>This function accepts zero or more arguments, each declared with the required type
-            <code>xs:anyAtomicType*</code>. The value <code>$v</code> supplied for each argument
-            is first reduced to a single string as follows:</p>
-         <ulist>
-            <item>
-               <p>If XPath 1.0 compatibility mode is set to true in the static context of the
-                  function call, then the result of <code>xs:string($v[1])</code>.</p>
-            </item>
-            <item>
-               <p>Otherwise, the result of <code>fn:string-join($v)</code>.</p>
-            </item>
-         </ulist>
-         <p>The resulting sequence of strings (one for each supplied argument) is then reduced
-            to a single string by applying <code>fn:string-join#1</code> to the sequence.</p>
-         <p>The <code>fn:concat</code> function is specified to allow zero or more arguments, which
-            are concatenated together. This is the only function specified in this document that
-            allows a variable number of arguments. This capability is retained for compatibility
-            with <bibref
-               ref="xpath"/>. </p>
+         <p>This function is defined to be variadic. It defines a single parameter with the required type
+            <code>xs:anyAtomicType*</code>, but because the function is variadic, 
+            the input sequence may be supplied using multiple arguments. In addition
+            the parameter is declared optional, so a call with no arguments is also permitted.</p>
+
+         <p>The result of the function is obtained by forming the sequence-concatenation of the supplied
+            argument values and applying the function <code>fn:string-join#0</code> to the result.</p>
+
+         <p>If XPath 1.0 compatibility mode is set to true in the static context of a
+            static function call to <code>fn:concat</code>, then each supplied argument 
+            <code>$v</code> is first reduced to a single
+            string, the result of the expression <code>xs:string($v[1])</code>. This is special-case
+            processing for the <code>fn:concat</code> function, it is not something
+            that follows from the general rules for calling variadic functions. This reflects the fact that
+            <code>fn:concat</code> had custom behavior in XPath 1.0. This rule applies only to
+            static function calls.</p>
+
       </fos:rules>
       <fos:notes>
          <p>As mentioned in <specref ref="string-types"
@@ -4191,6 +4202,9 @@ return normalize-unicode(concat($v1, $v2))</eg>
             (Unicode codepoint <code>U+0308</code>) or <code>&amp;#x0308;</code>, will return:</p>
          <p><code>"I plan to go to München in September"</code></p>
          <p>This returned result is normalized in NFC.</p>
+         <p>Alternatives to the <code>fn:concat</code> function include the concatenation operator
+         <code>||</code> (for example <code>$x || '-' || $y</code>), and the use of string templates 
+         (for example <code>`{$x}-{$y}`)</code>.</p>
       </fos:notes>
       <fos:examples>
          <fos:example>

specifications/xpath-functions-40/src/xpath-functions.xml

@@ -1165,6 +1165,11 @@ This includes all the built-in datatypes defined in <bibref ref="xmlschema-2"/>.
                repeated calls with the same explicit and implicit arguments <rfc2119>must</rfc2119> return
                identical results.</p>
 
+               <p><termdef id="dt-variadic" term="variadic">Several functions defined in this specification
+               are defined as variadic. This means that in a static function call, several arguments
+               in the function call can be sequence-concatenated to supply the value of a single parameter
+               in the function definition.</termdef></p>
+
             </div3>           
          </div2>
       </div1>

specifications/xquery-40/src/errors.xml

@@ -1115,6 +1115,15 @@ It is a static error if the name of a feature in
          are not compatible as defined in <xspecref spec="DM40" ref="schema-consistency"/>.</p>
       </error>
 
+      <error spec="XQ" role="xquery" code="0150" class="ST" type="static">
+         <p> It is a <termref def="dt-static-error">static error</termref> 
+            if any of the parameters in a variadic function declaration 
+            is declared as optional: that is, 
+            if a function declaration is annotated as
+            <code>%variadic</code> then none of its parameters may 
+            contain a <nt def="ParamWithDefault">ParamWithDefault</nt>.</p>
+      </error>
+
 
    </error-list>
 </div1>