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<body bgcolor="#ffffff"> <i>The Hugs 98 User Manual</i><br> <a href="index.html">top</a> | <a href="exts.html">back</a> | <a href="diffs.html">next</a> <br><hr>
<a name="otherps"></a><a name="sect8"></a>
<h2>8<tt> </tt>Other Hugs programs</h2>
The Hugs interpreter is available in two other guises: a
stand-alone system that executes programs in a `load and go' style,
without the surrounding command system; and a Windows user interface,
layered on top of the basic Hugs system.<p>
<a name="sect8.1"></a>
<h3>8.1<tt> </tt>Stand-alone program execution</h3>
Once a program has been developed and debugged, the Hugs command loop
can be eliminated and the program can be executed immediately without
any command to run it. A slightly modified version of the interpreter
called <tt>runhugs</tt> loads the literate program specified as its
first argument and runs <tt>main</tt> in module <tt>Main</tt>. Unlike the
standard Hugs system, <tt>runhugs</tt> makes command arguments available
to the running Hugs system. The first argument, specifying the
program, is removed from the argument list.<p>
On Unix systems, executable programs may be created by
placing <tt>runhugs</tt> in the first line of an executable file, like so:
<tt><br>
#!/hugs/runhugs<br>
<br>
> module Main where<br>
> main = putStr "Hello, World\n"<br>
</tt>Because <tt>runHugs</tt> uses literate Haskell only, the line starting
with <tt>#!</tt> is viewed as a comment. Stand-alone programs can
import other modules using import chasing---these modules need not be
literate. The <tt>runhugs</tt> program uses the same environment
variables to set Hugs options as the standard Hugs systems.
However, <tt>runhugs</tt> does not set options from the command line; all
command line options are passed into the executing Hugs program. The
stand-alone Hugs program may return an exit code.<p>
On Windows 95/NT, <tt>runhugs</tt> is invoked using a separate
file extension that is set up to call <tt>runhugs</tt> rather
than <tt>hugs</tt>. Installation sets up the <tt>.hsx</tt> extension for this
purpose. A <tt>.hsx</tt> program will run when it is clicked on;
a console window will appear if the program writes to standard output
or reads from standard input. This window is closed immedately upon
exiting the program. There is no way to pass parameters to
the <tt>.hsx</tt> program when it is double-clicked.
Windows 95/NT can also use <tt>runhugs</tt> to open files of a given
type; this involves setting the "open" command for the file type to
call <tt>runhugs</tt>, passing it the Haskell program to run and the
file being opened. The online documentation has some examples of
this.<p>
<a name="sect8.2"></a>
<h3>8.2<tt> </tt>Hugs for Windows</h3>
Hugs for Windows (<tt>winhugs</tt>) offers a GUI front-end to the
Hugs interpreter on Microsoft Windows platforms. The user interface
features a scrolling console window that mimics the normal Hugs
interface, together with a menu and toolbar that provide additional
facilities for browsing Haskell programs. Most of the additional
features are self-explanatory, although short descriptions of menu
and toolbar choices are displayed in a status line.
Hugs for Windows uses the same command line options and
environment/registry variables as Hugs. It also stores options in
a <tt>.ini</tt> file.<p>
The Hugs for Windows front-end is useful for beginners, but is not
compatible with the Win32 libraries or with programs that use them,
such as Conal Elliot's Fran system or Paul Hudak's Graphics library.
In addition, the current
implementation uses a compute-intensive polling process to detect
certain events, and this can incur a fairly substantial performance
penalty. For these reasons, the Hugs for Windows front-end is not
recommended for work on large projects.<p>
<hr><i>The Hugs 98 User Manual</i><br><a href="index.html">top</a> | <a href="exts.html">back</a> | <a href="diffs.html">next</a> <br><font size=2>May 22, 1999</font>
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