<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Hugs-specific language extensions</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="HOME" TITLE="The Hugs 98 User's Guide" HREF="index.html"><LINK REL="PREVIOUS" TITLE="Implicit parameters" HREF="implicit-parameters.html"><LINK REL="NEXT" TITLE="Restricted type synonyms" HREF="restricted-synonyms.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="hugs-ug.css"></HEAD ><BODY CLASS="CHAPTER" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >The Hugs 98 User's Guide</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="implicit-parameters.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="restricted-synonyms.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="CHAPTER" ><H1 ><A NAME="HUGS-ONLY" ></A >Chapter 7. Hugs-specific language extensions</H1 ><P >These experimental features are unique to Hugs. Except of the debugging primitives, they require the <CODE CLASS="OPTION" >-98</CODE > option.</P ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="TREX" >7.1. Typed records with extensibility</A ></H1 ><P ><ACRONYM CLASS="ACRONYM" >Trex</ACRONYM > is a very powerful and flexible record system. See <A HREF="http://cvs.haskell.org/Hugs/pages/hugsman/exts.html#sect7.2" TARGET="_top" >Section 7.2 of the <I CLASS="CITETITLE" >Hugs 98 User Manual</I ></A > for details.</P ><P >To use equality and <CODE CLASS="FUNCTION" >show</CODE > on extensible records, a module must import <TT CLASS="LITERAL" >Hugs.Trex</TT >. This module also defines an empty record value and type: <PRE CLASS="PROGRAMLISTING" >emptyRec :: Rec EmptyRow</PRE ></P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="implicit-parameters.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="restricted-synonyms.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Implicit parameters</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Restricted type synonyms</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
