Documentation for -fbreak-on-error

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

diff --git a/docs/users_guide/ghci.xml b/docs/users_guide/ghci.xml
index d3efd2a..b1e36ec 100644 (file)
--- a/docs/users_guide/ghci.xml
+++ b/docs/users_guide/ghci.xml
@@ -564,7 +564,7 @@ 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>

@@ -715,7 +715,7 @@ 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 +764,8 @@ 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>

@@ -788,7 +788,7 @@ def = toEnum 0
     <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

@@ -1017,7 +1017,7 @@ 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 +1080,7 @@ 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 +1106,14 @@ 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 +1122,11 @@ _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> is ommitted, then it single-steps from
         <replaceable>expr</replaceable> in single-stepping mode.  If
         <replaceable>expr</replaceable> is ommitted, then it single-steps from

-        the current breakpoint.</para>
+        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 +1335,13 @@ 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>
 

@@ -1488,7 +1497,7 @@ 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 +1525,7 @@ $ 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 +1541,7 @@ $ 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> 

@@ -1711,16 +1713,6 @@ $ 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 +1727,16 @@ $ 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>

@@ -1744,7 +1746,8 @@ $ 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
+           (<literal>:ctags</literal>) or
+        Emacs-style editors (<literal>:etags</literal>).  If

            no filename is specified, the defaulit <filename>tags</filename> or
            <filename>TAGS</filename> is
            used, respectively.  Tags for all the functions, constructors and
            no filename is specified, the defaulit <filename>tags</filename> or
            <filename>TAGS</filename> is
            used, respectively.  Tags for all the functions, constructors and

@@ -1852,6 +1855,15 @@ 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>

@@ -1920,6 +1932,12 @@ 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 +2006,7 @@ 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>

@@ -2033,7 +2051,7 @@ 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 +2071,7 @@ 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>

@@ -2198,7 +2216,7 @@ 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>
 
        </listitem>
       </varlistentry>
 

@@ -2309,7 +2327,7 @@ 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

@@ -2421,9 +2439,10 @@ 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>$HOME/.ghci</filename>, followed by
-    <filename>./.ghci</filename>.</para>
+    <para>When it starts, unless the <literal>-ignore-dot-ghci</literal>
+    flag is given, GHCi reads and executes commands from
+    <filename>./.ghci</filename>, followed by
+    <filename>$HOME/.ghci</filename>.</para>

 
     <para>The <filename>.ghci</filename> in your home directory is
     most useful for turning on favourite options (eg. <literal>:set
 
     <para>The <filename>.ghci</filename> in your home directory is
     most useful for turning on favourite options (eg. <literal>:set

@@ -2432,7 +2451,7 @@ Prelude> :set -fno-glasgow-exts
     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
     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
+    subdirectories A, B and C, you might put the following lines in

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

@@ -2580,7 +2599,19 @@ 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>