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>35.8. Internal Functions</A
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><P
>    Internal functions are functions written in C that have been statically
    linked into the <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> server.
    The <SPAN
CLASS="QUOTE"
>"body"</SPAN
> of the function definition
    specifies the C-language name of the function, which need not be the
    same as the name being declared for SQL use.
    (For reasons of backward compatibility, an empty body
    is accepted as meaning that the C-language function name is the
    same as the SQL name.)
   </P
><P
>    Normally, all internal functions present in the
    server are declared during the initialization of the database cluster
    (see <A
HREF="creating-cluster.html"
>Section 17.2</A
>),
    but a user could use <TT
CLASS="COMMAND"
>CREATE FUNCTION</TT
>
    to create additional alias names for an internal function.
    Internal functions are declared in <TT
CLASS="COMMAND"
>CREATE FUNCTION</TT
>
    with language name <TT
CLASS="LITERAL"
>internal</TT
>.  For instance, to
    create an alias for the <CODE
CLASS="FUNCTION"
>sqrt</CODE
> function:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE FUNCTION square_root(double precision) RETURNS double precision
    AS 'dsqrt'
    LANGUAGE internal
    STRICT;</PRE
><P>
    (Most internal functions expect to be declared <SPAN
CLASS="QUOTE"
>"strict"</SPAN
>.)
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>Note: </B
>     Not all <SPAN
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>"predefined"</SPAN
> functions are
     <SPAN
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>"internal"</SPAN
> in the above sense.  Some predefined
     functions are written in SQL.
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