FIX #1861: floating-point constants for infinity and NaN in via-C

[ghc-hetmet.git] / docs / users_guide / ghci.xml

diff --git a/docs/users_guide/ghci.xml b/docs/users_guide/ghci.xml
index d3efd2a..35aa7cd 100644 (file)
--- a/docs/users_guide/ghci.xml
+++ b/docs/users_guide/ghci.xml
@@ -368,7 +368,6 @@ hello
       <literal>IO</literal> monad.
 <screen>
 Prelude> x &lt;- return 42
       <literal>IO</literal> monad.
 <screen>
 Prelude> x &lt;- return 42

-42

 Prelude> print x
 42
 Prelude>
 Prelude> print x
 42
 Prelude>

@@ -380,7 +379,8 @@ Prelude>
       <literal>x</literal> in future statements, for example to print
       it as we did above.</para>
 
       <literal>x</literal> in future statements, for example to print
       it as we did above.</para>
 

-      <para>GHCi will print the result of a statement if and only if: 
+      <para>If <option>-fprint-bind-result</option> is set then
+      GHCi will print the result of a statement if and only if: 

        <itemizedlist>
          <listitem>
            <para>The statement is not a binding, or it is a monadic binding 
        <itemizedlist>
          <listitem>
            <para>The statement is not a binding, or it is a monadic binding 

@@ -393,13 +393,8 @@ Prelude>
              <literal>Show</literal></para>
          </listitem>
        </itemizedlist>
              <literal>Show</literal></para>
          </listitem>
        </itemizedlist>

-      The automatic printing of binding results can be supressed with
-      <option>:set -fno-print-bind-result</option> (this does not
-      supress printing the result of non-binding statements).
-      <indexterm><primary><option>-fno-print-bind-result</option></primary></indexterm><indexterm><primary><option>-fprint-bind-result</option></primary></indexterm>.
-      You might want to do this to prevent the result of binding
-      statements from being fully evaluated by the act of printing
-      them, for example.</para>
+      <indexterm><primary><option>-fprint-bind-result</option></primary></indexterm><indexterm><primary><option>-fno-print-bind-result</option></primary></indexterm>.
+      </para>

 
       <para>Of course, you can also bind normal non-IO expressions
       using the <literal>let</literal>-statement:</para>
 
       <para>Of course, you can also bind normal non-IO expressions
       using the <literal>let</literal>-statement:</para>

@@ -424,6 +419,45 @@ Prelude>
       <para>Note that <literal>let</literal> bindings do not automatically
        print the value bound, unlike monadic bindings.</para>
 
       <para>Note that <literal>let</literal> bindings do not automatically
        print the value bound, unlike monadic bindings.</para>
 

+      <para>Hint: you can also use <literal>let</literal>-statements
+      to define functions at the prompt:</para>
+<screen>
+Prelude> let add a b = a + b
+Prelude> add 1 2
+3
+Prelude>
+</screen>
+        <para>However, this quickly gets tedious when defining functions 
+        with multiple clauses, or groups of mutually recursive functions,
+        because the complete definition has to be given on a single line, 
+        using explicit braces and semicolons instead of layout:</para>
+<screen>
+Prelude> let { f op n [] = n ; f op n (h:t) = h `op` f op n t }
+Prelude> f (+) 0 [1..3]
+6
+Prelude>
+</screen>
+      <para>To alleviate this issue, GHCi commands can be split over
+      multiple lines, by wrapping them in <literal>:{</literal> and
+      <literal>:}</literal> (each on a single line of its own):</para>
+<screen>
+Prelude> :{
+Prelude| let { g op n [] = n
+Prelude|     ; g op n (h:t) = h `op` g op n t
+Prelude|     }
+Prelude| :}
+Prelude> g (*) 1 [1..3]
+6
+</screen>
+      <para>Such multiline commands can be used with any GHCi command,
+      and the lines between <literal>:{</literal> and
+      <literal>:}</literal> are simply merged into a single line for 
+      interpretation. That implies that each such group must form a single
+      valid command when merged, and that no layout rule is used. 
+      The main purpose of multiline commands is not to replace module
+      loading but to make definitions in .ghci-files (see <xref
+      linkend="ghci-dot-files"/>) more readable and maintainable.</para>
+

       <para>Any exceptions raised during the evaluation or execution
       of the statement are caught and printed by the GHCi command line
       interface (for more information on exceptions, see the module
       <para>Any exceptions raised during the evaluation or execution
       of the statement are caught and printed by the GHCi command line
       interface (for more information on exceptions, see the module

@@ -564,7 +598,7 @@ Prelude IO>
       <para>
         Hint: GHCi will tab-complete names that are in scope; for
         example, if you run GHCi and type <literal>J&lt;tab&gt;</literal>
       <para>
         Hint: GHCi will tab-complete names that are in scope; for
         example, if you run GHCi and type <literal>J&lt;tab&gt;</literal>

-        then GHCi will expand it to <literal>Just </literal>.
+        then GHCi will expand it to &ldquo;<literal>Just </literal>&rdquo;.

       </para>
 
       <sect3>
       </para>
 
       <sect3>

@@ -577,7 +611,7 @@ Prelude IO>
       </sect3>
 
       <sect3>
       </sect3>
 
       <sect3>

-        <title>The <literal>:main</literal> command</title>
+        <title>The <literal>:main</literal> and <literal>:run</literal> commands</title>

 
         <para>
           When a program is compiled and executed, it can use the
 
         <para>
           When a program is compiled and executed, it can use the

@@ -602,6 +636,37 @@ Prelude> :main foo bar
 ["foo","bar"]
 </screen>
 
 ["foo","bar"]
 </screen>
 

+        <para>
+            We can also quote arguments which contains characters like
+            spaces, and they are treated like Haskell strings, or we can
+            just use Haskell list syntax:
+        </para>
+
+<screen>
+Prelude> :main foo "bar baz"
+["foo","bar baz"]
+Prelude> :main ["foo", "bar baz"]
+["foo","bar baz"]
+</screen>
+
+        <para>
+            Finally, other functions can be called, either with the
+            <literal>-main-is</literal> flag or the <literal>:run</literal>
+            command:
+        </para>
+
+<screen>
+Prelude> let foo = putStrLn "foo" >> System.Environment.getArgs >>= print
+Prelude> let bar = putStrLn "bar" >> System.Environment.getArgs >>= print
+Prelude> :set -main-is foo
+Prelude> :main foo "bar baz"
+foo
+["foo","bar baz"]
+Prelude> :run bar ["foo", "bar baz"]
+bar
+["foo","bar baz"]
+</screen>
+

       </sect3>
     </sect2>
   
       </sect3>
     </sect2>
   

@@ -715,7 +780,7 @@ it &lt;- <replaceable>e</replaceable>
         </listitem>
     </orderedlist>
     At the GHCi prompt, or with GHC if the
         </listitem>
     </orderedlist>
     At the GHCi prompt, or with GHC if the

-    <literal>-fextended-default-rules</literal> flag is given,
+    <literal>-XExtendedDefaultRules</literal> flag is given,

     the following additional differences apply:
     <itemizedlist>
         <listitem>
     the following additional differences apply:
     <itemizedlist>
         <listitem>

@@ -764,8 +829,8 @@ def = toEnum 0
     instance that returns <literal>IO a</literal>.
     However, it is only able to return
     <literal>undefined</literal>
     instance that returns <literal>IO a</literal>.
     However, it is only able to return
     <literal>undefined</literal>

-    (the reason for the instance having this type is to not require
-    extensions to the class system), so if the type defaults to
+    (the reason for the instance having this type is so that printf
+    doesn't require extensions to the class system), so if the type defaults to

     <literal>Integer</literal> then ghci gives an error when running a
     printf.
    </para>
     <literal>Integer</literal> then ghci gives an error when running a
     printf.
    </para>

@@ -780,15 +845,17 @@ def = toEnum 0
     <para>GHCi contains a simple imperative-style debugger in which you can
       stop a running computation in order to examine the values of
       variables.  The debugger is integrated into GHCi, and is turned on by
     <para>GHCi contains a simple imperative-style debugger in which you can
       stop a running computation in order to examine the values of
       variables.  The debugger is integrated into GHCi, and is turned on by

-      default: no flags are required to enable the debugging facilities.  There
-      is one major restriction: breakpoints and single-stepping are only
-      available in <emphasis>interpreted</emphasis> modules; compiled code is
-      invisible to the debugger.</para>
+      default: no flags are required to enable the debugging
+      facilities.  There is one major restriction: breakpoints and
+      single-stepping are only available in interpreted modules;
+      compiled code is invisible to the debugger<footnote><para>Note that packages
+      only contain compiled code, so debugging a package requires
+      finding its source and loading that directly.</para></footnote>.</para>

 
     <para>The debugger provides the following:
     <itemizedlist>
         <listitem>
 
     <para>The debugger provides the following:
     <itemizedlist>
         <listitem>

-          <para>The abilty to set a <firstterm>breakpoint</firstterm> on a
+          <para>The ability to set a <firstterm>breakpoint</firstterm> on a

             function definition or expression in the program.  When the function
             is called, or the expression evaluated, GHCi suspends 
             execution and returns to the prompt, where you can inspect the
             function definition or expression in the program.  When the function
             is called, or the expression evaluated, GHCi suspends 
             execution and returns to the prompt, where you can inspect the

@@ -818,9 +885,12 @@ def = toEnum 0
     </para>
       
     <para>There is currently no support for obtaining a &ldquo;stack
     </para>
       
     <para>There is currently no support for obtaining a &ldquo;stack

-      trace&rdquo;, but the tracing and history features provide a useful
-      second-best, which will often be enough to establish the context of an
-      error.</para>
+    trace&rdquo;, but the tracing and history features provide a
+    useful second-best, which will often be enough to establish the
+    context of an error.  For instance, it is possible to break
+    automatically when an exception is thrown, even if it is thrown
+    from within compiled code (see <xref
+    linkend="ghci-debugger-exceptions" />).</para>

       
     <sect2 id="breakpoints">
       <title>Breakpoints and inspecting variables</title>
       
     <sect2 id="breakpoints">
       <title>Breakpoints and inspecting variables</title>

@@ -929,6 +999,7 @@ right :: [a]
         <literal>left</literal>:</para>
 
 <screen>
         <literal>left</literal>:</para>
 
 <screen>

+[qsort.hs:2:15-46] *Main> :set -fprint-evld-with-show

 [qsort.hs:2:15-46] *Main> :print left
 left = (_t1::[a])
 </screen>
 [qsort.hs:2:15-46] *Main> :print left
 left = (_t1::[a])
 </screen>

@@ -948,6 +1019,13 @@ left = (_t1::[a])
         underscore, in this case
         <literal>_t1</literal>.</para>
 
         underscore, in this case
         <literal>_t1</literal>.</para>
 

+      <para>The flag <literal>-fprint-evld-with-show</literal> instructs
+      <literal>:print</literal> to reuse
+      available <literal>Show</literal> instances when possible. This happens
+      only when the contents of the variable being inspected 
+      are completely evaluated.</para>
+
+

       <para>If we aren't concerned about preserving the evaluatedness of a
         variable, we can use <literal>:force</literal> instead of
         <literal>:print</literal>.  The <literal>:force</literal> command
       <para>If we aren't concerned about preserving the evaluatedness of a
         variable, we can use <literal>:force</literal> instead of
         <literal>:print</literal>.  The <literal>:force</literal> command

@@ -1017,7 +1095,8 @@ right :: [a]
       <para>The execution continued at the point it previously stopped, and has
         now stopped at the breakpoint for a second time.</para>
 
       <para>The execution continued at the point it previously stopped, and has
         now stopped at the breakpoint for a second time.</para>
 

-      <sect3 id="setting-breakpoings">
+
+      <sect3 id="setting-breakpoints">

         <title>Setting breakpoints</title>
 
         <para>Breakpoints can be set in various ways.  Perhaps the easiest way to
         <title>Setting breakpoints</title>
 
         <para>Breakpoints can be set in various ways.  Perhaps the easiest way to

@@ -1080,7 +1159,7 @@ right :: [a]
         <title>Listing and deleting breakpoints</title>
 
         <para>The list of breakpoints currently enabled can be displayed using
         <title>Listing and deleting breakpoints</title>
 
         <para>The list of breakpoints currently enabled can be displayed using

-          <literal>:show&nbsp;breaks</literal></para>:
+          <literal>:show&nbsp;breaks</literal>:</para>

 <screen>
 *Main> :show breaks
 [0] Main qsort.hs:1:11-12
 <screen>
 *Main> :show breaks
 [0] Main qsort.hs:1:11-12

@@ -1106,10 +1185,14 @@ right :: [a]
 
       <para>Single-stepping is a great way to visualise the execution of your
         program, and it is also a useful tool for identifying the source of a
 
       <para>Single-stepping is a great way to visualise the execution of your
         program, and it is also a useful tool for identifying the source of a

-        bug.  The concept is simple: single-stepping enables all the
-        breakpoints in the program and executes until the next breakpoint is
-        reached, at which point you can single-step again, or continue
-        normally.  For example:</para>
+        bug. GHCi offers two variants of stepping. Use 
+       <literal>:step</literal>  to enable all the
+        breakpoints in the program, and execute until the next breakpoint is
+        reached. Use <literal>:steplocal</literal> to limit the set
+       of enabled breakpoints to those in the current top level function.
+       Similarly, use <literal>:stepmodule</literal> to single step only on
+       breakpoints contained in the current module.
+       For example:</para>

 
 <screen>
 *Main> :step main
 
 <screen>
 *Main> :step main

@@ -1118,10 +1201,11 @@ _result :: IO ()
 </screen>
 
       <para>The command <literal>:step
 </screen>
 
       <para>The command <literal>:step

-          <replaceable>expr</replaceable></literal> begins the evaluation of
+        <replaceable>expr</replaceable></literal> begins the evaluation of

         <replaceable>expr</replaceable> in single-stepping mode.  If
         <replaceable>expr</replaceable> in single-stepping mode.  If

-        <replaceable>expr</replaceable> is ommitted, then it single-steps from
-        the current breakpoint.</para>
+        <replaceable>expr</replaceable> is omitted, then it single-steps from
+        the current breakpoint. <literal>:stepover</literal> 
+        works similarly.</para>

 
       <para>The <literal>:list</literal> command is particularly useful when
         single-stepping, to see where you currently are:</para>
 
       <para>The <literal>:list</literal> command is particularly useful when
         single-stepping, to see where you currently are:</para>

@@ -1330,9 +1414,13 @@ a :: a
         <literal>:trace</literal> and <literal>:history</literal> to establish
         the context.  However, <literal>head</literal> is in a library and
         we can't set a breakpoint on it directly.  For this reason, GHCi
         <literal>:trace</literal> and <literal>:history</literal> to establish
         the context.  However, <literal>head</literal> is in a library and
         we can't set a breakpoint on it directly.  For this reason, GHCi

-        provides the flag <literal>-fbreak-on-exception</literal> which causes
-        the evaluator to stop when an exception is thrown, just as it does when
-        a breakpoint is hit.  This is only really useful in conjunction with
+        provides the flags <literal>-fbreak-on-exception</literal> which causes
+        the evaluator to stop when an exception is thrown, and <literal>
+       -fbreak-on-error</literal>, which works similarly but stops only on 
+       uncaught exceptions. When stopping at an exception, GHCi will act 
+       just as it does when a breakpoint is hit, with the deviation that it
+       will not show you any source code location. Due to this, these 
+       commands are only really useful in conjunction with

         <literal>:trace</literal>, in order to log the steps leading up to the
         exception.  For example:</para>
 
         <literal>:trace</literal>, in order to log the steps leading up to the
         exception.  For example:</para>
 

@@ -1385,7 +1473,7 @@ as = 'b' : 'c' : (_t1::[Char])
 <programlisting>
 import Prelude hiding (map)
 
 <programlisting>
 import Prelude hiding (map)
 

-map :: (a->b) -> a -> b
+map :: (a->b) -> [a] -> [b]

 map f [] = []
 map f (x:xs) = f x : map f xs
 </programlisting>
 map f [] = []
 map f (x:xs) = f x : map f xs
 </programlisting>

@@ -1488,7 +1576,7 @@ Just 20
         </listitem>
        <listitem><para>
          Implicit parameters (see <xref linkend="implicit-parameters"/>) are only available 
         </listitem>
        <listitem><para>
          Implicit parameters (see <xref linkend="implicit-parameters"/>) are only available 

-         at the scope of a breakpoint if there is a explicit type signature.
+         at the scope of a breakpoint if there is an explicit type signature.

        </para>
         </listitem>
       </itemizedlist>
        </para>
         </listitem>
       </itemizedlist>

@@ -1516,9 +1604,7 @@ $ ghci Main.hs
 
     <para>Most of the command-line options accepted by GHC (see <xref
     linkend="using-ghc"/>) also make sense in interactive mode.  The ones
 
     <para>Most of the command-line options accepted by GHC (see <xref
     linkend="using-ghc"/>) also make sense in interactive mode.  The ones

-    that don't make sense are mostly obvious; for example, GHCi
-    doesn't generate interface files, so options related to interface
-    file generation won't have any effect.</para>
+    that don't make sense are mostly obvious.</para>

 
     <sect2>
       <title>Packages</title>
 
     <sect2>
       <title>Packages</title>

@@ -1534,12 +1620,7 @@ $ ghci Main.hs
 
 <screen>
 $ ghci -package readline
 
 <screen>
 $ ghci -package readline

-   ___         ___ _
-  / _ \ /\  /\/ __(_)
- / /_\// /_/ / /  | |      GHC Interactive, version 6.6, for Haskell 98.
-/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
-\____/\/ /_/\____/|_|      Type :? for help.
-
+GHCi, version 6.8.1: http://www.haskell.org/ghc/  :? for help

 Loading package base ... linking ... done.
 Loading package readline-1.0 ... linking ... done.
 Prelude> 
 Loading package base ... linking ... done.
 Loading package readline-1.0 ... linking ... done.
 Prelude> 

@@ -1669,22 +1750,58 @@ $ ghci -lm
 
       <varlistentry>
        <term>
 
       <varlistentry>
        <term>

-          <literal>:browse</literal> <optional><literal>*</literal></optional><replaceable>module</replaceable> ...
+          <literal>:browse</literal><optional><literal>!</literal></optional> <optional><optional><literal>*</literal></optional><replaceable>module</replaceable></optional> ...

           <indexterm><primary><literal>:browse</literal></primary></indexterm>
         </term>
        <listitem>
          <para>Displays the identifiers defined by the module
          <replaceable>module</replaceable>, which must be either
           <indexterm><primary><literal>:browse</literal></primary></indexterm>
         </term>
        <listitem>
          <para>Displays the identifiers defined by the module
          <replaceable>module</replaceable>, which must be either

-         loaded into GHCi or be a member of a package.  If the
-         <literal>*</literal> symbol is placed before the module
-         name, then <emphasis>all</emphasis> the identifiers defined
-         in <replaceable>module</replaceable> are shown; otherwise
-         the list is limited to the exports of
+         loaded into GHCi or be a member of a package.  If
+         <replaceable>module</replaceable> is omitted, the most
+         recently-loaded module is used.</para>
+
+          <para>If the <literal>*</literal> symbol is placed before
+         the module name, then <emphasis>all</emphasis> the
+         identifiers in scope in <replaceable>module</replaceable> are
+         shown; otherwise the list is limited to the exports of

          <replaceable>module</replaceable>.  The
          <literal>*</literal>-form is only available for modules
          which are interpreted; for compiled modules (including
          modules from packages) only the non-<literal>*</literal>
          <replaceable>module</replaceable>.  The
          <literal>*</literal>-form is only available for modules
          which are interpreted; for compiled modules (including
          modules from packages) only the non-<literal>*</literal>

-         form of <literal>:browse</literal> is available.</para>
+    form of <literal>:browse</literal> is available.
+    If the <literal>!</literal> symbol is appended to the
+    command, data constructors and class methods will be 
+    listed individually, otherwise, they will only be listed
+    in the context of their data type or class declaration. 
+    The <literal>!</literal>-form also annotates the listing 
+    with comments giving possible imports for each group of 
+    entries.</para>
+<screen>
+Prelude> :browse! Data.Maybe
+-- not currently imported
+Data.Maybe.catMaybes :: [Maybe a] -> [a]
+Data.Maybe.fromJust :: Maybe a -> a
+Data.Maybe.fromMaybe :: a -> Maybe a -> a
+Data.Maybe.isJust :: Maybe a -> Bool
+Data.Maybe.isNothing :: Maybe a -> Bool
+Data.Maybe.listToMaybe :: [a] -> Maybe a
+Data.Maybe.mapMaybe :: (a -> Maybe b) -> [a] -> [b]
+Data.Maybe.maybeToList :: Maybe a -> [a]
+-- imported via Prelude
+Just :: a -> Maybe a
+data Maybe a = Nothing | Just a
+Nothing :: Maybe a
+maybe :: b -> (a -> b) -> Maybe a -> b
+</screen>
+  <para>
+    This output shows that, in the context of the current session, in the scope
+    of <literal>Prelude</literal>, the first group of items from
+    <literal>Data.Maybe</literal> have not been imported (but are available in
+    fully qualified form in the GHCi session - see <xref
+      linkend="ghci-scope"/>), whereas the second group of items have been
+    imported via <literal>Prelude</literal> and are therefore available either
+    unqualified, or with a <literal>Prelude.</literal> qualifier.
+  </para>

        </listitem>
       </varlistentry>
 
        </listitem>
       </varlistentry>
 

@@ -1711,16 +1828,6 @@ $ ghci -lm
 
       <varlistentry>
        <term>
 
       <varlistentry>
        <term>

-          <literal>:continue</literal> 
-          <indexterm><primary><literal>:continue</literal></primary></indexterm>
-        </term>
-       <listitem><para>Continue the current evaluation, when stopped at a
-            breakpoint.</para>
-       </listitem>
-      </varlistentry>
-
-      <varlistentry>
-       <term>

           <literal>:cmd</literal> <replaceable>expr</replaceable>
           <indexterm><primary><literal>:cmd</literal></primary></indexterm>
         </term>
           <literal>:cmd</literal> <replaceable>expr</replaceable>
           <indexterm><primary><literal>:cmd</literal></primary></indexterm>
         </term>

@@ -1735,6 +1842,16 @@ $ ghci -lm
 
       <varlistentry>
        <term>
 
       <varlistentry>
        <term>

+          <literal>:continue</literal> 
+          <indexterm><primary><literal>:continue</literal></primary></indexterm>
+        </term>
+       <listitem><para>Continue the current evaluation, when stopped at a
+            breakpoint.</para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term>

          <literal>:ctags</literal> <optional><replaceable>filename</replaceable></optional>
          <literal>:etags</literal> <optional><replaceable>filename</replaceable></optional>
          <indexterm><primary><literal>:etags</literal></primary>
          <literal>:ctags</literal> <optional><replaceable>filename</replaceable></optional>
          <literal>:etags</literal> <optional><replaceable>filename</replaceable></optional>
          <indexterm><primary><literal>:etags</literal></primary>

@@ -1744,8 +1861,9 @@ $ ghci -lm
        </term>
        <listitem>
          <para>Generates a &ldquo;tags&rdquo; file for Vi-style editors
        </term>
        <listitem>
          <para>Generates a &ldquo;tags&rdquo; file for Vi-style editors

-           (<literal>:ctags</literal>) or Emacs-style editors (<literal>etags</literal>).  If
-           no filename is specified, the defaulit <filename>tags</filename> or
+           (<literal>:ctags</literal>) or
+        Emacs-style editors (<literal>:etags</literal>).  If
+           no filename is specified, the default <filename>tags</filename> or

            <filename>TAGS</filename> is
            used, respectively.  Tags for all the functions, constructors and
            types in the currently loaded modules are created.  All modules must
            <filename>TAGS</filename> is
            used, respectively.  Tags for all the functions, constructors and
            types in the currently loaded modules are created.  All modules must

@@ -1756,26 +1874,27 @@ $ ghci -lm
 
       <varlistentry>
        <term>
 
       <varlistentry>
        <term>

-          <literal>:def</literal> <replaceable>name</replaceable> <replaceable>expr</replaceable>
+          <literal>:def<optional>!</optional> <optional><replaceable>name</replaceable> <replaceable>expr</replaceable></optional></literal>

           <indexterm><primary><literal>:def</literal></primary></indexterm>
         </term>
        <listitem>
           <indexterm><primary><literal>:def</literal></primary></indexterm>
         </term>
        <listitem>

-         <para>The command <literal>:def</literal>
-         <replaceable>name</replaceable>
-         <replaceable>expr</replaceable> defines a new GHCi command
-         <literal>:<replaceable>name</replaceable></literal>,
-         implemented by the Haskell expression
-         <replaceable>expr</replaceable>, which must have type
-         <literal>String -> IO String</literal>.  When
-         <literal>:<replaceable>name</replaceable>
-         <replaceable>args</replaceable></literal> is typed at the
-         prompt, GHCi will run the expression
-         <literal>(<replaceable>name</replaceable>
-         <replaceable>args</replaceable>)</literal>, take the
-         resulting <literal>String</literal>, and feed it back into
-         GHCi as a new sequence of commands.  Separate commands in
-         the result must be separated by
-         &lsquo;<literal>\n</literal>&rsquo;.</para>
+          <para><literal>:def</literal> is used to define new
+          commands, or macros, in GHCi.  The command
+          <literal>:def</literal> <replaceable>name</replaceable>
+          <replaceable>expr</replaceable> defines a new GHCi command
+          <literal>:<replaceable>name</replaceable></literal>,
+          implemented by the Haskell expression
+          <replaceable>expr</replaceable>, which must have type
+          <literal>String -> IO String</literal>.  When
+          <literal>:<replaceable>name</replaceable>
+          <replaceable>args</replaceable></literal> is typed at the
+          prompt, GHCi will run the expression
+          <literal>(<replaceable>name</replaceable>
+          <replaceable>args</replaceable>)</literal>, take the
+          resulting <literal>String</literal>, and feed it back into
+          GHCi as a new sequence of commands.  Separate commands in
+          the result must be separated by
+          &lsquo;<literal>\n</literal>&rsquo;.</para>

 
          <para>That's all a little confusing, so here's a few
          examples.  To start with, here's a new GHCi command which
 
          <para>That's all a little confusing, so here's a few
          examples.  To start with, here's a new GHCi command which

@@ -1819,6 +1938,12 @@ Prelude> :. cmds.ghci
           <literal>:.</literal>, by analogy with the
           &lsquo;<literal>.</literal>&rsquo; Unix shell command that
           does the same thing.</para>
           <literal>:.</literal>, by analogy with the
           &lsquo;<literal>.</literal>&rsquo; Unix shell command that
           does the same thing.</para>

+
+          <para>Typing <literal>:def</literal> on its own lists the
+          currently-defined macros.  Attempting to redefine an
+          existing command name results in an error unless the
+          <literal>:def!</literal> form is used, in which case the old
+          command with that name is silently overwritten.</para>

        </listitem>
       </varlistentry>
 
        </listitem>
       </varlistentry>
 

@@ -1852,6 +1977,15 @@ Prelude> :. cmds.ghci
 
       <varlistentry>
        <term>
 
       <varlistentry>
        <term>

+          <literal>:etags</literal> 
+        </term>
+       <listitem>
+         <para>See <literal>:ctags</literal>.</para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term>

           <literal>:force <replaceable>identifier</replaceable> ...</literal>
           <indexterm><primary><literal>:force</literal></primary></indexterm>
         </term>
           <literal>:force <replaceable>identifier</replaceable> ...</literal>
           <indexterm><primary><literal>:force</literal></primary></indexterm>
         </term>

@@ -1893,6 +2027,17 @@ Prelude> :. cmds.ghci
       </varlistentry>
 
       <varlistentry>
       </varlistentry>
 
       <varlistentry>

+       <term>
+          <literal>:</literal>
+          <indexterm><primary><literal>:</literal></primary></indexterm>
+        </term>
+       <listitem>
+         <para>Repeat the previous command.</para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+

        <term>
           <literal>:history [<replaceable>num</replaceable>]</literal>
           <indexterm><primary><literal>:history</literal></primary></indexterm>
        <term>
           <literal>:history [<replaceable>num</replaceable>]</literal>
           <indexterm><primary><literal>:history</literal></primary></indexterm>

@@ -1920,6 +2065,12 @@ Prelude> :. cmds.ghci
          will be printed.  If <replaceable>name</replaceable> has
          been loaded from a source file, then GHCi will also display
          the location of its definition in the source.</para>
          will be printed.  If <replaceable>name</replaceable> has
          been loaded from a source file, then GHCi will also display
          the location of its definition in the source.</para>

+         <para>For types and classes, GHCi also summarises instances that
+         mention them.  To avoid showing irrelevant information, an instance
+         is shown only if (a) its head mentions <replaceable>name</replaceable>, 
+         and (b) all the other things mentioned in the instance
+         are in scope (either qualified or otherwise) as a result of 
+         a <literal>:load</literal> or <literal>:module</literal> commands. </para>

        </listitem>
       </varlistentry>
 
        </listitem>
       </varlistentry>
 

@@ -1988,7 +2139,7 @@ Prelude> :. cmds.ghci
             However, we cannot simply pass the arguments to the
             <literal>main</literal> function while we are testing in ghci,
             as the <literal>main</literal> function doesn't take its
             However, we cannot simply pass the arguments to the
             <literal>main</literal> function while we are testing in ghci,
             as the <literal>main</literal> function doesn't take its

-            directly.
+            arguments directly.

           </para>
 
           <para>
           </para>
 
           <para>

@@ -2004,6 +2155,37 @@ Prelude> :main foo bar
 ["foo","bar"]
 </screen>
 
 ["foo","bar"]
 </screen>
 

+        <para>
+            We can also quote arguments which contains characters like
+            spaces, and they are treated like Haskell strings, or we can
+            just use Haskell list syntax:
+        </para>
+
+<screen>
+Prelude> :main foo "bar baz"
+["foo","bar baz"]
+Prelude> :main ["foo", "bar baz"]
+["foo","bar baz"]
+</screen>
+
+        <para>
+            Finally, other functions can be called, either with the
+            <literal>-main-is</literal> flag or the <literal>:run</literal>
+            command:
+        </para>
+
+<screen>
+Prelude> let foo = putStrLn "foo" >> System.Environment.getArgs >>= print
+Prelude> let bar = putStrLn "bar" >> System.Environment.getArgs >>= print
+Prelude> :set -main-is foo
+Prelude> :main foo "bar baz"
+foo
+["foo","bar baz"]
+Prelude> :run bar ["foo", "bar baz"]
+bar
+["foo","bar baz"]
+</screen>
+

         </listitem>
       </varlistentry>
 
         </listitem>
       </varlistentry>
 

@@ -2033,7 +2215,7 @@ Prelude> :main foo bar
        <listitem>
          <para>Prints a value without forcing its evaluation.
             <literal>:print</literal> may be used on values whose types are
        <listitem>
          <para>Prints a value without forcing its evaluation.
             <literal>:print</literal> may be used on values whose types are

-            unkonwn or partially known, which might be the case for local
+            unknown or partially known, which might be the case for local

             variables with polymorphic types at a breakpoint.  While inspecting
             the runtime value, <literal>:print</literal> attempts to
             reconstruct the type of the value, and will elaborate the type in
             variables with polymorphic types at a breakpoint.  While inspecting
             the runtime value, <literal>:print</literal> attempts to
             reconstruct the type of the value, and will elaborate the type in

@@ -2053,7 +2235,7 @@ Prelude> :main foo bar
           <indexterm><primary><literal>:quit</literal></primary></indexterm>
         </term>
        <listitem>
           <indexterm><primary><literal>:quit</literal></primary></indexterm>
         </term>
        <listitem>

-         <para>Quits GHCi.  You can also quit by typing a control-D
+         <para>Quits GHCi.  You can also quit by typing control-D

          at the prompt.</para>
        </listitem>
       </varlistentry>
          at the prompt.</para>
        </listitem>
       </varlistentry>

@@ -2078,10 +2260,11 @@ Prelude> :main foo bar
           <indexterm><primary><literal>:set</literal></primary></indexterm>
         </term>
        <listitem>
           <indexterm><primary><literal>:set</literal></primary></indexterm>
         </term>
        <listitem>

-         <para>Sets various options.  See <xref linkend="ghci-set"/>
-         for a list of available options.  The
-         <literal>:set</literal> command by itself shows which
-         options are currently set.</para>
+    <para>Sets various options.  See <xref linkend="ghci-set"/> for a list of
+      available options and <xref linkend="interactive-mode-options"/> for a
+      list of GHCi-specific flags.  The <literal>:set</literal> command by
+      itself shows which options are currently set. It also lists the current
+      dynamic flag settings, with GHCi-specific flags listed separately.</para>

        </listitem>
       </varlistentry>
 
        </listitem>
       </varlistentry>
 

@@ -2198,12 +2381,34 @@ Prelude> :main foo bar
           <indexterm><primary><literal>:show modules</literal></primary></indexterm>
         </term>
        <listitem>
           <indexterm><primary><literal>:show modules</literal></primary></indexterm>
         </term>
        <listitem>

-         <para>Show the list of modules currently load.</para>
+         <para>Show the list of modules currently loaded.</para>

        </listitem>
       </varlistentry>
 
       <varlistentry>
        <term>
        </listitem>
       </varlistentry>
 
       <varlistentry>
        <term>

+          <literal>:show packages</literal>
+          <indexterm><primary><literal>:show packages</literal></primary></indexterm>
+        </term>
+       <listitem>
+    <para>Show the currently active package flags, as well as the list of
+      packages currently loaded.</para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term>
+          <literal>:show languages</literal>
+          <indexterm><primary><literal>:show languages</literal></primary></indexterm>
+        </term>
+       <listitem>
+    <para>Show the currently active language flags.</para>
+       </listitem>
+      </varlistentry>
+
+
+      <varlistentry>
+       <term>

           <literal>:show [args|prog|prompt|editor|stop]</literal>
           <indexterm><primary><literal>:show</literal></primary></indexterm>
         </term>
           <literal>:show [args|prog|prompt|editor|stop]</literal>
           <indexterm><primary><literal>:show</literal></primary></indexterm>
         </term>

@@ -2309,7 +2514,7 @@ Prelude> :main foo bar
 
     <para>The <literal>:set</literal> command sets two types of
     options: GHCi options, which begin with
 
     <para>The <literal>:set</literal> command sets two types of
     options: GHCi options, which begin with

-    &lsquo;<literal>+</literal>&rdquo; and &ldquo;command-line&rdquo;
+    &lsquo;<literal>+</literal>&rsquo;, and &ldquo;command-line&rdquo;

     options, which begin with &lsquo;-&rsquo;.  </para>
 
     <para>NOTE: at the moment, the <literal>:set</literal> command
     options, which begin with &lsquo;-&rsquo;.  </para>
 
     <para>NOTE: at the moment, the <literal>:set</literal> command

@@ -2421,18 +2626,35 @@ Prelude> :set -fno-glasgow-exts
     <indexterm><primary>startup</primary><secondary>files, GHCi</secondary>
     </indexterm>
 
     <indexterm><primary>startup</primary><secondary>files, GHCi</secondary>
     </indexterm>
 

-    <para>When it starts, GHCi always reads and executes commands from
-    <filename>$HOME/.ghci</filename>, followed by
-    <filename>./.ghci</filename>.</para>
-
-    <para>The <filename>.ghci</filename> in your home directory is
-    most useful for turning on favourite options (eg. <literal>:set
-    +s</literal>), and defining useful macros.  Placing a
-    <filename>.ghci</filename> file in a directory with a Haskell
-    project is a useful way to set certain project-wide options so you
-    don't have to type them everytime you start GHCi: eg. if your
-    project uses GHC extensions and CPP, and has source files in three
-    subdirectories A B and C, you might put the following lines in
+    <para>When it starts, unless the <literal>-ignore-dot-ghci</literal>
+    flag is given, GHCi reads and executes commands from the following
+    files, in this order, if they exist:</para>
+
+    <orderedlist>
+    <listitem>
+      <para><filename>./.ghci</filename></para>
+    </listitem>
+    <listitem>
+      <para><literal><replaceable>appdata</replaceable>/ghc/ghci.conf</literal>,
+      where <replaceable>appdata</replaceable> depends on your system,
+      but is usually something like <literal>C:/Documents and Settings/<replaceable>user</replaceable>/Application Data</literal></para>
+    </listitem>
+    <listitem>
+      <para>On Unix: <literal>$HOME/.ghc/ghci.conf</literal></para>
+    </listitem>
+    <listitem>
+      <para><literal>$HOME/.ghci</literal></para>
+    </listitem>
+   </orderedlist>
+
+    <para>The <filename>ghci.conf</filename> file is most useful for
+    turning on favourite options (eg. <literal>:set +s</literal>), and
+    defining useful macros.  Placing a <filename>.ghci</filename> file
+    in a directory with a Haskell project is a useful way to set
+    certain project-wide options so you don't have to type them
+    everytime you start GHCi: eg. if your project uses GHC extensions
+    and CPP, and has source files in three subdirectories A, B and C,
+    you might put the following lines in

     <filename>.ghci</filename>:</para>
 
 <screen>
     <filename>.ghci</filename>:</para>
 
 <screen>

@@ -2446,7 +2668,7 @@ Prelude> :set -fno-glasgow-exts
     until the next <literal>:load</literal>, though.)</para>
 
     <para>Two command-line options control whether the
     until the next <literal>:load</literal>, though.)</para>
 
     <para>Two command-line options control whether the

-    <filename>.ghci</filename> files are read:</para>
+    startup files files are read:</para>

 
     <variablelist>
       <varlistentry>
 
     <variablelist>
       <varlistentry>

@@ -2455,8 +2677,8 @@ Prelude> :set -fno-glasgow-exts
           <indexterm><primary><option>-ignore-dot-ghci</option></primary></indexterm>
         </term>
        <listitem>
           <indexterm><primary><option>-ignore-dot-ghci</option></primary></indexterm>
         </term>
        <listitem>

-         <para>Don't read either <filename>./.ghci</filename> or
-         <filename>$HOME/.ghci</filename> when starting up.</para>
+         <para>Don't read either <filename>./.ghci</filename> or the
+          other startup files when starting up.</para>

        </listitem>
       </varlistentry>
       <varlistentry>
        </listitem>
       </varlistentry>
       <varlistentry>

@@ -2465,8 +2687,8 @@ Prelude> :set -fno-glasgow-exts
           <indexterm><primary><option>-read-dot-ghci</option></primary></indexterm>
         </term>
        <listitem>
           <indexterm><primary><option>-read-dot-ghci</option></primary></indexterm>
         </term>
        <listitem>

-         <para>Read <filename>.ghci</filename> and
-         <filename>$HOME/.ghci</filename>.  This is normally the
+         <para>Read <filename>./.ghci</filename> and the other
+          startup files (see above).  This is normally the

          default, but the <option>-read-dot-ghci</option> option may
          be used to override a previous
          <option>-ignore-dot-ghci</option> option.</para>
          default, but the <option>-read-dot-ghci</option> option may
          be used to override a previous
          <option>-ignore-dot-ghci</option> option.</para>

@@ -2580,7 +2802,19 @@ Prelude> :set -fno-glasgow-exts
        <term>I can't use Control-C to interrupt computations in
           GHCi on Windows.</term>
         <listitem>
        <term>I can't use Control-C to interrupt computations in
           GHCi on Windows.</term>
         <listitem>

-          <para>See <xref linkend="ghci-windows"/></para>
+          <para>See <xref linkend="ghci-windows"/>.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term>The default buffering mode is different in GHCi to GHC.</term>
+        <listitem>
+          <para>
+            In GHC, the stdout handle is line-buffered by default.
+            However, in GHCi we turn off the buffering on stdout,
+            because this is normally what you want in an interpreter:
+            output appears as it is generated.
+          </para>

         </listitem>
       </varlistentry>
     </variablelist>
         </listitem>
       </varlistentry>
     </variablelist>