<?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>Control/Monad/Trans.hs</title> <link type='text/css' rel='stylesheet' href='hscolour.css' /> </head> <body> <pre><a name="line-1"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span> <a name="line-2"></a><span class='hs-comment'>-- |</span> <a name="line-3"></a><span class='hs-comment'>-- Module : Control.Monad.Trans</span> <a name="line-4"></a><span class='hs-comment'>-- Copyright : (c) Andy Gill 2001,</span> <a name="line-5"></a><span class='hs-comment'>-- (c) Oregon Graduate Institute of Science and Technology, 2001</span> <a name="line-6"></a><span class='hs-comment'>-- License : BSD-style (see the file LICENSE)</span> <a name="line-7"></a><span class='hs-comment'>--</span> <a name="line-8"></a><span class='hs-comment'>-- Maintainer : libraries@haskell.org</span> <a name="line-9"></a><span class='hs-comment'>-- Stability : experimental</span> <a name="line-10"></a><span class='hs-comment'>-- Portability : portable</span> <a name="line-11"></a><span class='hs-comment'>--</span> <a name="line-12"></a><span class='hs-comment'>-- Classes for monad transformers.</span> <a name="line-13"></a><span class='hs-comment'>--</span> <a name="line-14"></a><span class='hs-comment'>-- A monad transformer makes new monad out of an existing monad, such</span> <a name="line-15"></a><span class='hs-comment'>-- that computations of the old monad may be embedded in the new one.</span> <a name="line-16"></a><span class='hs-comment'>-- To construct a monad with a desired set of features, one typically</span> <a name="line-17"></a><span class='hs-comment'>-- starts with a base monad, such as @Identity@, @[]@ or 'IO', and</span> <a name="line-18"></a><span class='hs-comment'>-- applies a sequence of monad transformers.</span> <a name="line-19"></a><span class='hs-comment'>--</span> <a name="line-20"></a><span class='hs-comment'>-- Most monad transformer modules include the special case of applying the</span> <a name="line-21"></a><span class='hs-comment'>-- transformer to @Identity@. For example, @State s@ is an abbreviation</span> <a name="line-22"></a><span class='hs-comment'>-- for @StateT s Identity@.</span> <a name="line-23"></a><span class='hs-comment'>--</span> <a name="line-24"></a><span class='hs-comment'>-- Each monad transformer also comes with an operation @run@/XXX/ to</span> <a name="line-25"></a><span class='hs-comment'>-- unwrap the transformer, exposing a computation of the inner monad.</span> <a name="line-26"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span> <a name="line-27"></a> <a name="line-28"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span> <span class='hs-layout'>(</span> <a name="line-29"></a> <span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Class</span><span class='hs-layout'>,</span> <a name="line-30"></a> <span class='hs-keyword'>module</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span><span class='hs-varop'>.</span><span class='hs-conid'>Class</span> <a name="line-31"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span> <a name="line-32"></a> <a name="line-33"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>IO</span><span class='hs-varop'>.</span><span class='hs-conid'>Class</span> <a name="line-34"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Class</span> </pre></body> </html>