[ch07 return coverage and tweaks
John Goerzen <jgoerzen@complete.org>**20071011071551] {
hunk ./en/ch07-io.xml 240
-      computation, you must use &return; to wrap it in &IO;.
+      computation, you must use &return; to wrap it in &IO;.  For more
+      details on &return;, see <xref linkend="hs.io.return"/>.
hunk ./en/ch07-io.xml 967
-        The call to <literal>printitall</literal>; finally executes all those actions.  Actually,
+        The call to <literal>printitall</literal> finally executes all those actions.  Actually,
hunk ./en/ch07-io.xml 1054
+    <sect2 id="hs.io.return">
+      <title>The True Nature of Return</title>
+      <para>
+        Earlier in this chapter, we mentioned that &return; is probably not
+        what it looks like.  Many languages have a keyword named &return;
+        that aborts execution of a function immediately and returns a value
+        to the caller.
+      </para>
+      <para>
+        The Haskell &return; function is quite different.  In Haskell,
+        &return; is used to wrap data in a monad.  When speaking about I/O,
+        &return; is used to take pure data and bring it into the IO monad.
+      </para>
+      <para>
+        Now, why would we want to do that?  Remember that anything whose
+        result depends on I/O must be within the IO monad.  So if we are
+        writing a function that performs I/O, then a pure computation, we
+        will need to use &return; to make this pure computation the proper
+        return value of the the function.  Otherwise, a type error would
+        occur.  Here's an example:
+      </para>
+    </sect2>
+
+
hunk ./examples/ch07/actions.hs 2
--- ch06/actions.hs
+-- ch07/actions.hs
hunk ./examples/ch07/actions2.hs 2
--- ch06/actions2.hs
+-- ch07/actions2.hs
hunk ./examples/ch07/basicio-nodo.hs 2
--- ch06/basicio-nodo.hs
+-- ch07/basicio-nodo.hs
hunk ./examples/ch07/basicio.hs 2
--- ch06/basicio.hs
+-- ch07/basicio.hs
hunk ./examples/ch07/callingpure.hs 2
--- ch06/callingpure.hs
+-- ch07/callingpure.hs
hunk ./examples/ch07/filter.hs 2
--- ch06/filter.hs
+-- ch07/filter.hs
hunk ./examples/ch07/tempfile.hs 2
--- ch06/tempfile.hs
+-- ch07/tempfile.hs
hunk ./examples/ch07/toupper-imp.hs 2
--- ch06/toupper-imp.hs
+-- ch07/toupper-imp.hs
hunk ./examples/ch07/toupper-lazy1.hs 2
--- ch06/toupper-lazy1.hs
+-- ch07/toupper-lazy1.hs
hunk ./examples/ch07/toupper-lazy2.hs 2
--- ch06/toupper-lazy2.hs
+-- ch07/toupper-lazy2.hs
hunk ./examples/ch07/toupper-lazy3.hs 2
--- ch06/toupper-lazy3.hs
+-- ch07/toupper-lazy3.hs
hunk ./examples/ch07/toupper-lazy4.hs 2
--- ch06/toupper-lazy4.hs
+-- ch07/toupper-lazy4.hs
hunk ./examples/ch07/toupper-lazy5.hs 2
--- ch06/toupper-lazy5.hs
+-- ch07/toupper-lazy5.hs
hunk ./examples/ch07/toupper-lazy6.hs 2
--- ch06/toupper-lazy6.hs
+-- ch07/toupper-lazy6.hs
}