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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<title>Help</title>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta content="37.444542, -122.161050" name="ICBM" />
<link media="all" href="/stylesheets/nu.css" type ="text/css" rel="stylesheet" />
</head>
<body>
<div id="container">
<div id="header">
<div style="float:left; margin-right:10px">
<img src="/files/recycle-s.png" height="50" alt="recycling symbol" />
</div>
<div style="float:left">
<h1><a href="/">Programming Nu</a></h1>
<h3><a href="https://github.com/programming-nu">github.com/programming-nu</a></h3>
</div>
</div>
<div id="content">
<div class="atomentry">
<div class="content" style="margin-bottom:10px">
<h1>Getting and Providing Help</h1>
<p>Nu includes a simple built-in help system.</p>
</div>
<div class="extended">
<p>All objects derived from NSObject support the "help" message,
which returns an NSString presenting help information for
the object.</p>
<p>You can use this from Nu by either sending the help message
to an object or by using the help operator. Here's an example
showing the use of the help operator:</p>
<pre>
% (help 99)
This is an instance of NSCFNumber.
% (help (NSApplication sharedApplication))
This is an instance of NSApplication.
</pre>
<p>This gets more interesting when we override the help method for
specific subclasses. In nu/help.nu there are definitions of help
methods for most of the built-in Nu operators. Here are some
examples:</p>
<pre>
% (help do)
This operator is used to create blocks.
For example, the following expression creates a
block that returns the sum of its two arguments:
(do (x y)
(+ x y))
% (help set)
This operator sets the value of a symbol to the result of an
expression evaluation.
% (help help)
This operator gets the help text for an object.
</pre>
<p>In that last case, the help operator is being called with itself
as an argument. While this appears indistinguishable from
sending the help message to the help object, the Nu precedence
policy is for lists beginning with operators to be treated as
operator calls and not message sends. To send the help message
to the help object, use the send operator as follows:</p>
<pre>
% (send help help)
This operator gets the help text for an object.
</pre>
<p>In the future, more mechanisms for adding help information
will be built into Nu. In the meantime, you can provide
help information for any of your objects by simply adding
the following method to your classes:</p>
<pre>
- (NSString *) help;
</pre>
</div>
</div> <!-- atomentry -->
</div> <!-- content -->
<div id="sidebar">
<div class="sidebar-node">
<h2><a href="/about">About Nu</a></h2>
</div>
<div class="sidebar-node">
<h2><a href="http://groups.google.com/group/programming-nu/topics">Google Group:<br/>Programming Nu</a></h2>
</div>
<div class="sidebar-node">
<h2><a href="/downloads">Download Nu</a></h2>
</div>
<div class="sidebar-node">
<h2>Git Repositories</h2>
<ul>
<li><a href="http://github.com/programming-nu/nu">nu</a></li>
<li><a href="http://github.com/programming-nu/programming-nu">programming-nu</a></li>
</ul>
</div>
<div class="sidebar-node">
<h2><a href="/documentation">Documentation</a></h2>
<ul>
<li><a href="/installing">Installing Nu</a></li>
<li><a href="/usage">Using Nu</a></li>
<li><a href="/embedding">Embedding Nu</a></li>
<li><a href="/reference">Nu Reference</a></li>
<li><a href="/syntax">- Syntax</a></li>
<li><a href="/operators">- Operators</a></li>
<li><a href="/types">- Types</a></li>
<li><a href="/doc/index.html">- Class Reference</a></li>
<li><a href="/help">Getting and Providing Help</a></li>
<li><a href="/debugging">Debugging Nu Programs</a></li>
<li><a href="/textmate">A Bundle for TextMate Users</a></li>
</ul>
</div>
<div class="sidebar-node">
<h2><a href="/examples">Examples</a></h2>
<ul>
<li><a href="/randomapp">RandomApp</a></li>
<li><a href="/randomappwithnibfile">RandomAppWithNibFile</a></li>
<li><a href="/currencyconverter">Currency Converter</a></li>
<li><a href="/nurocks">NuRocks</a></li>
<li><a href="/console">Console</a></li>
<li><a href="/growler">Growler</a></li>
<li><a href="/benwanu">Benwanu</a></li>
<li><a href="/screensaver">Screen Saver</a></li>
<li><a href="/maildemo">MailDemo</a></li>
<li><a href="/nuanywhere">NuAnywhere</a></li>
</ul>
</div>
<div class="sidebar-node">
<h2><a href="/tools">Tools</a></h2>
<ul>
<li><a href="/nuke">nuke, a make utility</a></li>
<li><a href="/nubile">nubile, a code formatter</a></li>
<li><a href="/nutest">nutest, a testing tool</a></li>
<li><a href="/nudoc">nudoc, a documentation generator</a></li>
<li><a href="/nutemplate">nutemplate, a templating tool</a></li>
<li><a href="/nubake">nubake, a code generation tool</a></li>
</ul>
</div>
<div class="sidebar-node">
<h2><a href="/">Archives</a></h2>
<ul>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">July 2019</li>
<li>
<a href="/posts/2019/07/25/programming-nu-on-github">
Programming Nu on GitHub</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">April 2013</li>
<li>
<a href="/posts/2013/04/14/Nu-2.1.0">
Nu-2.1.0</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">September 2011</li>
<li>
<a href="/posts/2011/09/02/Nu-2.0.1">
Nu-2.0.1</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">August 2011</li>
<li>
<a href="/posts/2011/08/25/Nu-2.0.0">
Nu-2.0.0</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">December 2009</li>
<li>
<a href="/posts/2009/12/09/stability">
Nu Seems Stable (by Jason Grossman)</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">November 2009</li>
<li>
<a href="/posts/2009/11/22/vi">
vi tips for Nu</a>
</li>
<li>
<a href="/posts/2009/11/17/Nu-0.4.0">
Nu-0.4.0</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">January 2009</li>
<li>
<a href="/posts/2009/01/02/macros">
Macros</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">December 2008</li>
<li>
<a href="/posts/2008/12/03/Nu-0.3.3">
Nu-0.3.3</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">June 2008</li>
<li>
<a href="/posts/2008/06/08/Nu-0.3.2">
Nu-0.3.2</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">May 2008</li>
<li>
<a href="/posts/2008/05/23/cocoa-programming-with-nu">
Cocoa Programming with Nu</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">March 2008</li>
<li>
<a href="/posts/2008/03/24/Nu-0.3.1">
Nu-0.3.1</a>
</li>
<li>
<a href="/posts/2008/03/21/announcing-nu">
Announcing Nu: The Video</a>
</li>
<li>
<a href="/posts/2008/03/18/nu-on-github">
Nu on github</a>
</li>
<li>
<a href="/posts/2008/03/14/new-platforms">
Linux and the iPhone</a>
</li>
<li>
<a href="/posts/2008/03/12/new-license">
Apache License, v. 2.0</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">February 2008</li>
<li>
<a href="/posts/2008/02/13/Nu-0.3.0">
Nu-0.3.0</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">December 2007</li>
<li>
<a href="/posts/2007/12/12/nupagepacker">
NuPagePacker</a>
</li>
<li>
<a href="/posts/2007/12/12/Nu-0.2.4">
Nu-0.2.4</a>
</li>
<li>
<a href="/posts/2007/12/07/Nu-0.2.3">
Nu-0.2.3</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">November 2007</li>
<li>
<a href="/posts/2007/11/26/Nu-0.2.2">
Nu-0.2.2</a>
</li>
<li>
<a href="/posts/2007/11/25/a-delicious-nu-screencast">
A Delicious Nu Screencast</a>
</li>
<li>
<a href="/posts/2007/11/12/Nu-0.2.1">
Nu-0.2.1</a>
</li>
<li style="font-weight:bold; font-size:smaller; background:#eee; line-height:100%">October 2007</li>
<li>
<a href="/posts/2007/10/17/new-literal-forms-in-nu">
New Literal Forms in Nu</a>
</li>
<li>
<a href="/posts/2007/10/17/escape-sequences-in-nu-strings">
Escape Sequences in Nu Strings</a>
</li>
<li>
<a href="/posts/2007/10/17/closures-in-nu">
Closures in Nu</a>
</li>
<li>
<a href="/posts/2007/10/17/Nu-0.2.0">
Nu-0.2.0</a>
</li>
<li>
<a href="/posts/2007/10/11/screen-savers-and-plugins">
Screen Savers and Plugins</a>
</li>
<li>
<a href="/posts/2007/10/10/markdown-in-nu">
Markdown in Nu</a>
</li>
<li>
<a href="/posts/2007/10/05/functional-nu">
Functional Aspects of Nu</a>
</li>
<li>
<a href="/posts/2007/10/04/randomapp-with-nibfile">
New Example: Nib Files</a>
</li>
<li>
<a href="/posts/2007/10/01/welcome">
Welcome</a>
</li>
</ul>
</div>
<div class="sidebar-node">
<h2><a href="/legal">Legal Details</a></h2>
</div>
</div> <!-- sidebar -->
</div><!-- container -->
</body>
</html>