<replaceable>expr</replaceable> is ommitted, then it single-steps from
the current breakpoint. <literal>:stepover</literal>
works similarly.</para>
-
- <para>In the current version of the debugger, <literal>:stepover</literal>
- is limited to work locally in the lexical sense, that is in the context
- of the current expression body.
- When you run to the end of the expression, <literal>:stepover</literal>
- stops working and switches to behave like regular <literal>:step</literal>.
- This means
- that it will fail to step over the last function application. As a result,
- currently <literal>:stepover</literal> works great for monadic code, but
- interacts less perfectly with pure code. For example, if stopped at the
- line 2, on the entire expression
- <literal>qsort left ++ [a] ++ qsort right</literal>:</para>
-<screen>
-... [qsort2.hs:2:15-46] *Main> :step
-Stopped at qsort2.hs:2:15-46
-
-... [qsort2.hs:2:15-46] *Main> :list
-2 qsort (a:as) = qsort left ++ [a] ++ qsort right
-</screen>
-
- <para> The first <literal>:stepover</literal> will step over the first
- <literal>qsort</literal> recursive call, as expected. The second one
- will step over the evaluation of <literal>[a]</literal>, again as
- expected. However, the third one has lexically <quote>run out</quote>
- of the current expression, and will behave like regular
- <literal>:step</literal>, performing one step of lazy evaluation and
- stopping at the next breakpoint. In this case it is indeed the second
- recursive application of <literal>qsort</literal>.</para>
-<screen>
-[qsort2.hs:2:36-46] *Main> :stepover
-Warning: no more breakpoints in this function body, switching to :step
-Stopped at qsort2.hs:(1,0)-(3,55)
-
-[qsort2.hs:2:36-46] *Main> :list
-_result :: [a]
-1 qsort [] = []
-2 qsort (a:as) = qsort left ++ [a] ++ qsort right
-3 where (left,right) = (filter (<=a) as, filter (>a) as)
-</screen>
+
<para>The <literal>:list</literal> command is particularly useful when
- single-stepping, to see where you currently are, as just shown
- in the above example.</para>
+ single-stepping, to see where you currently are:</para>
<screen>
[qsort.hs:5:7-47] *Main> :list
CAF (e.g. main), stop at a breakpoint, and ask for the value of the
CAF at the prompt again.</para>
</listitem>
- <listitem> <literal>:stepover</literal> only works lexically locally, in the
- body of the current expression. As a result, it can be rather impredictable
- when used in pure functional code, as opposed to monadic code.
- </listitem>
<listitem><para>
Implicit parameters (see <xref linkend="implicit-parameters"/>) are only available
at the scope of a breakpoint if there is an explicit type signature.