<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <!--Rendered using the Haskell Html Library v0.2--> <HTML ><HEAD ><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=UTF-8" ><TITLE >Data.Text.Lazy.Read</TITLE ><LINK HREF="haddock.css" REL="stylesheet" TYPE="text/css" ><SCRIPT SRC="haddock-util.js" TYPE="text/javascript" ></SCRIPT ><SCRIPT TYPE="text/javascript" >window.onload = function () {setSynopsis("mini_Data-Text-Lazy-Read.html")};</SCRIPT ></HEAD ><BODY ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD CLASS="topbar" ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD ><IMG SRC="haskell_icon.gif" WIDTH="16" HEIGHT="16" ALT=" " ></TD ><TD CLASS="title" >text-0.10.0.0: An efficient packed Unicode text type.</TD ><TD CLASS="topbut" ><A HREF="src/Data-Text-Lazy-Read.html" >Source code</A ></TD ><TD CLASS="topbut" ><A HREF="index.html" >Contents</A ></TD ><TD CLASS="topbut" ><A HREF="doc-index.html" >Index</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="modulebar" ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD ><FONT SIZE="6" >Data.Text.Lazy.Read</FONT ></TD ><TD ALIGN="right" ><TABLE CLASS="narrow" CELLSPACING="0" CELLPADDING="0" ><TR ><TD CLASS="infohead" >Portability</TD ><TD CLASS="infoval" >GHC</TD ></TR ><TR ><TD CLASS="infohead" >Stability</TD ><TD CLASS="infoval" >experimental</TD ></TR ><TR ><TD CLASS="infohead" >Maintainer</TD ><TD CLASS="infoval" >bos@serpentine.com, rtomharper@googlemail.com, duncan@haskell.org</TD ></TR ></TABLE ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" >Description</TD ></TR ><TR ><TD CLASS="doc" >Functions used frequently when reading textual data. </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" >Synopsis</TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="body" ><TABLE CLASS="vanilla" CELLSPACING="0" CELLPADDING="0" ><TR ><TD CLASS="decl" ><SPAN CLASS="keyword" >type</SPAN > <A HREF="#t%3AReader" >Reader</A > a = <A HREF="Data-Text-Lazy.html#t%3AText" >Text</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Either.html#t%3AEither" >Either</A > <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A > (a, <A HREF="Data-Text-Lazy.html#t%3AText" >Text</A >)</TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3Adecimal" >decimal</A > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AIntegral" >Integral</A > a => <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a</TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3Ahexadecimal" >hexadecimal</A > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AIntegral" >Integral</A > a => <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a</TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3Asigned" >signed</A > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3ANum" >Num</A > a => <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a -> <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a</TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3Arational" >rational</A > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3ARealFloat" >RealFloat</A > a => <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a</TD ></TR ><TR ><TD CLASS="s8" ></TD ></TR ><TR ><TD CLASS="decl" ><A HREF="#v%3Adouble" >double</A > :: <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3ADouble" >Double</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="section1" >Documentation</TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><SPAN CLASS="keyword" >type</SPAN > <A NAME="t:Reader" ><A NAME="t%3AReader" ></A ></A ><B >Reader</B > a = <A HREF="Data-Text-Lazy.html#t%3AText" >Text</A > -> <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Either.html#t%3AEither" >Either</A > <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Data-Char.html#t%3AString" >String</A > (a, <A HREF="Data-Text-Lazy.html#t%3AText" >Text</A >)</TD ><TD CLASS="declbut" ><A HREF="src/Data-Text-Lazy-Read.html#Reader" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" >Read some text. If the read succeeds, return its value and the remaining text, otherwise an error message. </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:decimal" ><A NAME="v%3Adecimal" ></A ></A ><B >decimal</B > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AIntegral" >Integral</A > a => <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a</TD ><TD CLASS="declbut" ><A HREF="src/Data-Text-Lazy-Read.html#decimal" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Read a decimal integer. The input must begin with at least one decimal digit, and is consumed until a non-digit or end of string is reached. </P ><P >This function does not handle leading sign characters. If you need to handle signed input, use <TT ><TT ><A HREF="Data-Text-Lazy-Read.html#v%3Asigned" >signed</A ></TT > <TT ><A HREF="Data-Text-Lazy-Read.html#v%3Adecimal" >decimal</A ></TT ></TT >. </P ><P ><EM >Note</EM >: For fixed-width integer types, this function does not attempt to detect overflow, so a sufficiently long input may give incorrect results. </P ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:hexadecimal" ><A NAME="v%3Ahexadecimal" ></A ></A ><B >hexadecimal</B > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3AIntegral" >Integral</A > a => <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a</TD ><TD CLASS="declbut" ><A HREF="src/Data-Text-Lazy-Read.html#hexadecimal" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Read a hexadecimal integer, consisting of an optional leading <TT >"0x"</TT > followed by at least one decimal digit. Input is consumed until a non-hex-digit or end of string is reached. This function is case insensitive. </P ><P >This function does not handle leading sign characters. If you need to handle signed input, use <TT ><TT ><A HREF="Data-Text-Lazy-Read.html#v%3Asigned" >signed</A ></TT > <TT ><A HREF="Data-Text-Lazy-Read.html#v%3Ahexadecimal" >hexadecimal</A ></TT ></TT >. </P ><P ><EM >Note</EM >: For fixed-width integer types, this function does not attempt to detect overflow, so a sufficiently long input may give incorrect results. </P ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:signed" ><A NAME="v%3Asigned" ></A ></A ><B >signed</B > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3ANum" >Num</A > a => <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a -> <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a</TD ><TD CLASS="declbut" ><A HREF="src/Data-Text-Lazy-Read.html#signed" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" >Read an optional leading sign character (<TT >'-'</TT > or <TT >'+'</TT >) and apply it to the result of applying the given reader. </TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:rational" ><A NAME="v%3Arational" ></A ></A ><B >rational</B > :: <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3ARealFloat" >RealFloat</A > a => <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > a</TD ><TD CLASS="declbut" ><A HREF="src/Data-Text-Lazy-Read.html#rational" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Read a rational number. </P ><P >This function accepts an optional leading sign character, followed by at least one decimal digit. The syntax similar to that accepted by the <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Text-Read.html#v%3Aread" >read</A ></TT > function, with the exception that a trailing <TT >'.'</TT > or <TT >'e'</TT > <EM >not</EM > followed by a number is not consumed. </P ><P >Examples: </P ><PRE >rational "3" == Right (3.0, "") rational "3.1" == Right (3.1, "") rational "3e4" == Right (30000.0, "") rational "3.1e4" == Right (31000.0, "") rational ".3" == Left "input does not start with a digit" rational "e3" == Left "input does not start with a digit" </PRE ><P >Examples of differences from <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Text-Read.html#v%3Aread" >read</A ></TT >: </P ><PRE >rational "3.foo" == Right (3.0, ".foo") rational "3e" == Right (3.0, "e") </PRE ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="topdecl" ><TABLE CLASS="declbar" ><TR ><TD CLASS="declname" ><A NAME="v:double" ><A NAME="v%3Adouble" ></A ></A ><B >double</B > :: <A HREF="Data-Text-Lazy-Read.html#t%3AReader" >Reader</A > <A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3ADouble" >Double</A ></TD ><TD CLASS="declbut" ><A HREF="src/Data-Text-Lazy-Read.html#double" >Source</A ></TD ></TR ></TABLE ></TD ></TR ><TR ><TD CLASS="doc" ><P >Read a rational number. </P ><P >The syntax accepted by this function is the same as for <TT ><A HREF="Data-Text-Lazy-Read.html#v%3Arational" >rational</A ></TT >. </P ><P ><EM >Note</EM >: This function is almost ten times faster than <TT ><A HREF="Data-Text-Lazy-Read.html#v%3Arational" >rational</A ></TT >, but is slightly less accurate. </P ><P >The <TT ><A HREF="/usr/share/doc/ghc/html/libraries/base-4.2.0.2/Prelude.html#t%3ADouble" >Double</A ></TT > type supports about 16 decimal places of accuracy. For 94.2% of numbers, this function and <TT ><A HREF="Data-Text-Lazy-Read.html#v%3Arational" >rational</A ></TT > give identical results, but for the remaining 5.8%, this function loses precision around the 15th decimal place. For 0.001% of numbers, this function will lose precision at the 13th or 14th decimal place. </P ></TD ></TR ><TR ><TD CLASS="s15" ></TD ></TR ><TR ><TD CLASS="botbar" >Produced by <A HREF="http://www.haskell.org/haddock/" >Haddock</A > version 2.6.1</TD ></TR ></TABLE ></BODY ></HTML >