Update docs for 7.4 array features and polymorphic functions.

This is Joe Conway's patch of 7-Aug plus further editorializing
of my own.

doc/src/sgml/syntax.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.80 2003/08/04 14:00:14 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/syntax.sgml,v 1.81 2003/08/09 22:50:22 tgl Exp $
 -->
 
 <chapter id="sql-syntax">
@@ -867,7 +867,8 @@ SELECT 3 OPERATOR(pg_catalog.+) 4;
 
     <listitem>
      <para>
-      A positional parameter reference, in the body of a function definition.
+      A positional parameter reference, in the body of a function definition
+      or prepared statement.
      </para>
     </listitem>
 
@@ -901,6 +902,12 @@ SELECT 3 OPERATOR(pg_catalog.+) 4;
      </para>
     </listitem>
 
+    <listitem>
+     <para>
+      An array constructor.
+     </para>
+    </listitem>
+
     <listitem>
      <para>
       Another value expression in parentheses, useful to group subexpressions and override precedence.
@@ -1216,8 +1223,86 @@ SELECT name, (SELECT max(pop) FROM cities WHERE cities.state = states.name)
    </para>
   </sect2>
 
+  <sect2 id="sql-syntax-array-constructors">
+   <title>Array Constructors</title>
+
+    <indexterm>
+     <primary>arrays</primary>
+     <secondary>constructors</secondary>
+    </indexterm>
+
+   <para>
+    An <firstterm>array constructor</> is an expression that builds an
+    array value from values for its member elements.  A simple array
+    constructor 
+    consists of the keyword <literal>ARRAY</literal>, a left square bracket
+    <literal>[</>, one or more expressions (separated by commas) for the
+    array element values, and finally a right square bracket <literal>]</>.
+    For example,
+<programlisting>
+SELECT ARRAY[1,2,3+4];
+  array
+---------
+ {1,2,7}
+(1 row)
+</programlisting>
+    The array element type is the common type of the member expressions,
+    determined using the same rules as for <literal>UNION</> or
+    <literal>CASE</> constructs (see <xref linkend="typeconv-union-case">). 
+   </para>
+
+   <para>
+    Multidimensional array values can be built by nesting array
+    constructors.
+    In the inner constructors, the keyword <literal>ARRAY</literal> may
+    be omitted.  For example, these produce the same result:
+
+<programlisting>
+SELECT ARRAY[ARRAY[1,2], ARRAY[3,4]];
+     array
+---------------
+ {{1,2},{3,4}}
+(1 row)
+
+SELECT ARRAY[[1,2],[3,4]];
+     array
+---------------
+ {{1,2},{3,4}}
+(1 row)
+</programlisting>
+
+    Since multidimensional arrays must be rectangular, inner constructors
+    at the same level must produce sub-arrays of identical dimensions.
+  </para>
+
+  <para>
+   It is also possible to construct an array from the results of a
+   subquery.  In this form, the array constructor is written with the
+   keyword <literal>ARRAY</literal> followed by a parenthesized (not
+   bracketed) subquery. For example:
+<programlisting>
+SELECT ARRAY(SELECT oid FROM pg_proc WHERE proname LIKE 'bytea%');
+                          ?column?
+-------------------------------------------------------------
+ {2011,1954,1948,1952,1951,1244,1950,2005,1949,1953,2006,31}
+(1 row)
+</programlisting>
+  The sub-select must return a single column. The
+  resulting one-dimensional array will have an element for each row in the
+  sub-select result, with an element type matching that of the sub-select's
+  output column.
+  </para>
+
+  <para>
+   The subscripts of an array value built with <literal>ARRAY</literal>
+   always begin with one.  For more information about arrays, see
+   <xref linkend="arrays">.
+  </para>
+
+  </sect2>
+
   <sect2 id="syntax-express-eval">
-   <title>Expression Evaluation</title>
+   <title>Expression Evaluation Rules</title>
 
    <para>
     The order of evaluation of subexpressions is not defined.  In