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diff --git a/doc/gf-refman.html b/doc/gf-refman.html index 376689a9a..d82fa9488 100644 --- a/doc/gf-refman.html +++ b/doc/gf-refman.html @@ -5,7 +5,7 @@ </HEAD><BODY BGCOLOR="white" TEXT="black"> <P ALIGN="center"><CENTER><H1>GF Language Reference Manual</H1> <FONT SIZE="4"> -<I>Aarne Ranta</I>, <I>Krasimir Angelov</I><BR>November 2013 +<I>Aarne Ranta</I>, <I>Krasimir Angelov</I><BR>June 2014, GF 3.6 </FONT></CENTER> <P></P> @@ -2490,8 +2490,20 @@ The result is a record type or a record with a union of the fields of <I>R</I> a </P> <UL> <LI>both <I>R</I> and <I>S</I> are either records or record types -<LI>the labels in <I>R</I> and <I>S</I> are distinct +<LI>the labels in <I>R</I> and <I>S</I> are disjoint, if <I>R</I> and <I>S</I> are record types </UL> +(Since GF version 3.6) If <I>R</I> and <I>S</I> are record objects, +then the labels in them need not be disjoint. Labels defined in +<I>S</I> are then given priority, so that record extensions in fact +works as <B>record update</B>. A common pattern of using this feature +is +<pre> + lin F x ... = x ** {r = ... x.r ...} +</pre> +where <tt>x</tt> is a record with many fields, just one of which is +updated. Following the normal binding conditions, <tt>x.r</tt> on the +right hand side still refers to the old value of the <tt>r</tt> field. + <A NAME="toc41"></A> <H3>Subtyping</H3> |