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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
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<title>The GHC Commentary - Prelude Foundations</title>
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<h1>The GHC Commentary - Prelude Foundations</h1>
<p>
The standard Haskell Prelude as well as GHC's Prelude extensions are
constructed from GHC's <a href="primitives.html">primitives</a> in a
couple of layers.
<h4><code>PrelBase.lhs</code></h4>
<p>
Some most elementary Prelude definitions are collected in <a
href="http://cvs.haskell.org/cgi-bin/cvsweb.cgi/fptools/ghc/lib/std/PrelBase.lhs"><code>PrelBase.lhs</code></a>.
In particular, it defines the boxed versions of Haskell primitive types
- for example, <code>Int</code> is defined as
<blockquote><pre>
data Int = I# Int#</pre>
</blockquote>
<p>
Saying that a boxed integer <code>Int</code> is formed by applying the
data constructor <code>I#</code> to an <em>unboxed</em> integer of type
<code>Int#</code>. Unboxed types are hardcoded in the compiler and
exported together with the <a href="primitives.html">primitive
operations</a> understood by GHC.
<p>
<code>PrelBase.lhs</code> similarly defines basic types, such as,
boolean values
<blockquote><pre>
data Bool = False | True deriving (Eq, Ord)</pre>
</blockquote>
<p>
the unit type
<blockquote><pre>
data () = ()</pre>
</blockquote>
<p>
and lists
<blockquote><pre>
data [] a = [] | a : [a]</pre>
</blockquote>
<p>
It also contains instance delarations for these types. In addition,
<code>PrelBase.lhs</code> contains some <a href="prelude.html">tricky
machinery</a> for efficient list handling.
<p><small>
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Last modified: Wed Aug 8 19:30:18 EST 2001
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