<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Loading and editing Haskell module files</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="UP" TITLE="Using Hugs" HREF="using-hugs.html"><LINK REL="PREVIOUS" TITLE="Using Hugs" HREF="using-hugs.html"><LINK REL="NEXT" TITLE="Getting information" HREF="info-commands.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="hugs-ug.css"></HEAD ><BODY CLASS="SECT1" 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="using-hugs.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 2. Using Hugs</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="info-commands.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="MODULE-COMMANDS" >2.2. Loading and editing Haskell module files</A ></H1 ><P >The Hugs prompt accepts expressions, but not Haskell definitions. These should be placed in text files containing Haskell modules, and these modules loaded into Hugs either by listing them on the command line, or by using the commands listed here. Hugs assumes that each Haskell module is in a separate file. You can load these files by name, or by specifying a module name.</P ><P >Hugs maintains a notion of a <I CLASS="FIRSTTERM" >current module</I >, initially the empty module <TT CLASS="LITERAL" >Hugs</TT > and normally indicated by the prompt. Expressions presented to Hugs are interpreted within the scope of the current module, i.e. they may refer to unexported names within the module.</P ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT ><A NAME="LOAD-COMMAND" ></A ><P ><B CLASS="COMMAND" >:load</B > [<TT CLASS="REPLACEABLE" ><I >file-or-module</I ></TT >...]</P ></DT ><DD ><P >Clear all files except the empty module <TT CLASS="LITERAL" >Hugs</TT >, the Haskell 98 <TT CLASS="LITERAL" >Prelude</TT > and modules it uses, and then load the specified files or modules (if any). The last module loaded becomes the current module.</P ><P >You may specify a literal filename. The named file may contain a Haskell module with any name, but you can't load two modules with the same name together. To include a literal space in a filename, either precede it with a backslash or wrap the whole filename double quotes. Double quoted filenames may also contain the escape sequences <SPAN CLASS="QUOTE" >"<TT CLASS="LITERAL" >\ </TT >"</SPAN >, <SPAN CLASS="QUOTE" >"<TT CLASS="LITERAL" >\"</TT >"</SPAN > and <SPAN CLASS="QUOTE" >"<TT CLASS="LITERAL" >\\</TT >"</SPAN >. Other backslashes are interpreted literally.</P ><P >When asked to load a module <TT CLASS="REPLACEABLE" ><I >M</I ></TT >, Hugs looks for a file <TT CLASS="FILENAME" ><TT CLASS="REPLACEABLE" ><I >dir</I ></TT >/<TT CLASS="REPLACEABLE" ><I >M</I ></TT >.hs</TT > or <TT CLASS="FILENAME" ><TT CLASS="REPLACEABLE" ><I >dir</I ></TT >/<TT CLASS="REPLACEABLE" ><I >M</I ></TT >.lhs</TT >, where <TT CLASS="REPLACEABLE" ><I >dir</I ></TT > is a directory in its search path. (The <SPAN CLASS="QUOTE" >"<TT CLASS="LITERAL" >/</TT >"</SPAN > is used on Unix systems; Windows systems use <SPAN CLASS="QUOTE" >"<TT CLASS="LITERAL" >\</TT >"</SPAN >.) The search path may be changed using the <A HREF="options.html#OPTION-SEARCH-PATH" ><CODE CLASS="OPTION" >-P</CODE ></A > option, while the set of suffixes tried may be changed using the <A HREF="options.html#OPTION-SUFFIXES" ><CODE CLASS="OPTION" >-S</CODE ></A > option (see <A HREF="options.html#OPTIONS-LOADING" >Section 3.1.2</A >). The file found should contain a Haskell module called <TT CLASS="REPLACEABLE" ><I >M</I ></TT >.</P ><P >In mapping compound module names like <TT CLASS="LITERAL" >A.B.C</TT > to files, the dots are interpreted as slashes, leading to filenames <TT CLASS="FILENAME" ><TT CLASS="REPLACEABLE" ><I >dir</I ></TT >/A/B/C.hs</TT > or <TT CLASS="FILENAME" ><TT CLASS="REPLACEABLE" ><I >dir</I ></TT >/A/B/C.lhs</TT >.</P ><P >Modules imported by Haskell modules are resolved to filenames in the same way, except that an extra directory is searched first when</P ><P ></P ><UL ><LI ><P >the importing module was loaded by specifying a filename in that directory, or</P ></LI ><LI ><P >the importing module was found relative to that directory.</P ></LI ></UL ><P >This fits nicely with the scenario where you load a module <PRE CLASS="SCREEN" >Hugs> :load /path/to/my/project/code.hs Main></PRE > where the directory <TT CLASS="LITERAL" >/path/to/my/project</TT > contains other modules used directly or indirectly by the module <TT CLASS="LITERAL" >Main</TT > in <TT CLASS="FILENAME" >code.hs</TT >. For example, suppose <TT CLASS="LITERAL" >Main</TT > imports <TT CLASS="LITERAL" >A.B.C</TT >, which in turn imports <TT CLASS="LITERAL" >D</TT >. These may be resolved to filenames <TT CLASS="FILENAME" >/path/to/my/project/A/B/C.hs</TT >, and (assuming that is found), <TT CLASS="FILENAME" >/path/to/my/project/D.hs</TT >. However imports from modules found on the search path do not use the extra directory.</P ></DD ><DT ><A NAME="ALSO-COMMAND" ></A ><P ><B CLASS="COMMAND" >:also</B > [<TT CLASS="REPLACEABLE" ><I >file-or-module</I ></TT >...]</P ></DT ><DD ><P >Read the specified additional files or modules. The last module loaded becomes the current module.</P ></DD ><DT ><A NAME="RELOAD-COMMAND" ></A ><P ><B CLASS="COMMAND" >:reload</B > </P ></DT ><DD ><P >Clear all files except the empty module <TT CLASS="LITERAL" >Hugs</TT >, the Haskell 98 <TT CLASS="LITERAL" >Prelude</TT > and modules it uses, and then reload all the previously loaded modules.</P ></DD ><DT ><A NAME="MODULE-COMMAND" ></A ><P ><B CLASS="COMMAND" >:module</B > <TT CLASS="REPLACEABLE" ><I >module</I ></TT > </P ></DT ><DD ><P >Set the current module for evaluating expressions.</P ></DD ><DT ><A NAME="EDIT-COMMAND" ></A ><P ><B CLASS="COMMAND" >:edit</B > [<TT CLASS="REPLACEABLE" ><I >file</I ></TT >]</P ></DT ><DD ><P >The <B CLASS="COMMAND" >:edit</B > command starts an editor program to modify or view a Haskell module. Hugs suspends until the editor terminates, and then reloads the currently loaded modules. The <CODE CLASS="OPTION" >-E</CODE > option (see <A HREF="options.html#OPTIONS-EDITOR" >Section 3.1.3</A >) can be used to configure Hugs to your editor of choice.</P ><P >If no filename is specified, Hugs edits the current module.</P ></DD ><DT ><A NAME="FIND-COMMAND" ></A ><P ><B CLASS="COMMAND" >:find</B > <TT CLASS="REPLACEABLE" ><I >name</I ></TT > </P ></DT ><DD ><P >Edit the module containing the definition of <TT CLASS="REPLACEABLE" ><I >name</I ></TT >.</P ></DD ></DL ></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="using-hugs.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="info-commands.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Using Hugs</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="using-hugs.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Getting information</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
