<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<!-- Generated by HsColour, http://www.cs.york.ac.uk/fp/darcs/hscolour/ -->
<title>GHC/Err.lhs</title>
<link type='text/css' rel='stylesheet' href='hscolour.css' />
</head>
<body>
\begin{code}
<pre><a name="line-1"></a><span class='hs-comment'>{-# OPTIONS_GHC -XNoImplicitPrelude #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# OPTIONS_HADDOCK hide #-}</span>
<a name="line-3"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-4"></a><span class='hs-comment'>-- |</span>
<a name="line-5"></a><span class='hs-comment'>-- Module : GHC.Err</span>
<a name="line-6"></a><span class='hs-comment'>-- Copyright : (c) The University of Glasgow, 1994-2002</span>
<a name="line-7"></a><span class='hs-comment'>-- License : see libraries/base/LICENSE</span>
<a name="line-8"></a><span class='hs-comment'>-- </span>
<a name="line-9"></a><span class='hs-comment'>-- Maintainer : cvs-ghc@haskell.org</span>
<a name="line-10"></a><span class='hs-comment'>-- Stability : internal</span>
<a name="line-11"></a><span class='hs-comment'>-- Portability : non-portable (GHC extensions)</span>
<a name="line-12"></a><span class='hs-comment'>--</span>
<a name="line-13"></a><span class='hs-comment'>-- The "GHC.Err" module defines the code for the wired-in error functions,</span>
<a name="line-14"></a><span class='hs-comment'>-- which have a special type in the compiler (with \"open tyvars\").</span>
<a name="line-15"></a><span class='hs-comment'>-- </span>
<a name="line-16"></a><span class='hs-comment'>-- We cannot define these functions in a module where they might be used</span>
<a name="line-17"></a><span class='hs-comment'>-- (e.g., "GHC.Base"), because the magical wired-in type will get confused</span>
<a name="line-18"></a><span class='hs-comment'>-- with what the typechecker figures out.</span>
<a name="line-19"></a><span class='hs-comment'>-- </span>
<a name="line-20"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-21"></a>
<a name="line-22"></a><span class='hs-comment'>-- #hide</span>
<a name="line-23"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Err</span>
<a name="line-24"></a> <span class='hs-layout'>(</span>
<a name="line-25"></a> <span class='hs-varid'>absentErr</span> <span class='hs-comment'>-- :: a</span>
<a name="line-26"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>divZeroError</span> <span class='hs-comment'>-- :: a</span>
<a name="line-27"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>overflowError</span> <span class='hs-comment'>-- :: a</span>
<a name="line-28"></a>
<a name="line-29"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>error</span> <span class='hs-comment'>-- :: String -> a</span>
<a name="line-30"></a>
<a name="line-31"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>undefined</span> <span class='hs-comment'>-- :: a</span>
<a name="line-32"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-33"></a>
<a name="line-34"></a><span class='hs-cpp'>#ifndef __HADDOCK__</span>
<a name="line-35"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Types</span>
<a name="line-36"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>GHC</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span>
<a name="line-37"></a><span class='hs-cpp'>#endif</span>
</pre>\end{code}
%*********************************************************
%* *
\subsection{Error-ish functions}
%* *
%*********************************************************
\begin{code}
<pre><a name="line-1"></a><a name="error"></a><span class='hs-comment'>-- | 'error' stops execution and displays an error message.</span>
<a name="line-2"></a><span class='hs-definition'>error</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Char</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>a</span>
<a name="line-3"></a><span class='hs-definition'>error</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>throw</span> <span class='hs-layout'>(</span><span class='hs-conid'>ErrorCall</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-4"></a>
<a name="line-5"></a><span class='hs-comment'>-- | A special case of 'error'.</span>
<a name="line-6"></a><span class='hs-comment'>-- It is expected that compilers will recognize this and insert error</span>
<a name="line-7"></a><span class='hs-comment'>-- messages which are more appropriate to the context in which 'undefined'</span>
<a name="line-8"></a><span class='hs-comment'>-- appears. </span>
<a name="line-9"></a>
<a name="line-10"></a><a name="undefined"></a><span class='hs-definition'>undefined</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span>
<a name="line-11"></a><span class='hs-definition'>undefined</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>error</span> <span class='hs-str'>"Prelude.undefined"</span>
</pre>\end{code}
%*********************************************************
%* *
\subsection{Compiler generated errors + local utils}
%* *
%*********************************************************
Used for compiler-generated error message;
encoding saves bytes of string junk.
\begin{code}
<pre><a name="line-1"></a><a name="absentErr"></a><span class='hs-definition'>absentErr</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-definition'>absentErr</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>error</span> <span class='hs-str'>"Oops! The program has entered an `absent' argument!\n"</span>
</pre>\end{code}
Divide by zero and arithmetic overflow.
We put them here because they are needed relatively early
in the libraries before the Exception type has been defined yet.
\begin{code}
<pre><a name="line-1"></a><a name="divZeroError"></a><span class='hs-comment'>{-# NOINLINE divZeroError #-}</span>
<a name="line-2"></a><span class='hs-definition'>divZeroError</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span>
<a name="line-3"></a><span class='hs-definition'>divZeroError</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>throw</span> <span class='hs-conid'>DivideByZero</span>
<a name="line-4"></a>
<a name="line-5"></a><a name="overflowError"></a><span class='hs-comment'>{-# NOINLINE overflowError #-}</span>
<a name="line-6"></a><span class='hs-definition'>overflowError</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span>
<a name="line-7"></a><span class='hs-definition'>overflowError</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>throw</span> <span class='hs-conid'>Overflow</span>
</pre>\end{code}
</body>
</html>
