From ce717da44a2b2190471731a8c3f80413134a07fd Mon Sep 17 00:00:00 2001
From: Martin Goik <goik@hdm-stuttgart.de>
Date: Tue, 1 Apr 2014 07:49:56 +0200
Subject: [PATCH] Exercise preperation enum
---
Sd1/swd1.xml | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 94 insertions(+), 2 deletions(-)
diff --git a/Sd1/swd1.xml b/Sd1/swd1.xml
index 3aad882f9..7340a2428 100644
--- a/Sd1/swd1.xml
+++ b/Sd1/swd1.xml
@@ -454,8 +454,53 @@
allows for setting the direction a wombat is going to move. Call
it inserting different values by right clicking on a wombat
instance. How do entered values relate to directions of a
- wombat's movement? You may evaluate the result by actually
- watching its moving direction. Is there another way?</para>
+ wombat's movement? Complete the following table by adding North,
+ South, East and West accordingly:</para>
+
+ <informaltable border="1" width="40%">
+ <colgroup width="45%"/>
+
+ <colgroup width="55%"/>
+
+ <tr>
+ <th>Integer value</th>
+
+ <th>Direction</th>
+ </tr>
+
+ <tr>
+ <td>0</td>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td>1</td>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td>2</td>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td>3</td>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td>other</td>
+
+ <td/>
+ </tr>
+ </informaltable>
+
+ <para>You may evaluate the result by actually watching its
+ moving direction. Is there another way?</para>
<para>Hint: The <productname>Greenfoot</productname> framework
allows you to inspect an object's internal attribute
@@ -519,6 +564,53 @@
</answer>
</qandaentry>
</qandadiv>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Representing directions by integer values ranging from 1
+ to 4 may be considered error prone. Explain possible
+ problems.</para>
+
+ <para>Hint: The <productname>Greenfoot</productname>
+ <filename>leaves-and-wombats</filename> scenario code contains
+ statements like <code>setDirection(EAST)</code>. But what about
+ <code>setDirection(35)</code> ?</para>
+ </question>
+
+ <answer>
+ <glosslist>
+ <para>A programmer may consistently use the predefined integer
+ values <code>EAST</code>, <code>WEST</code>,
+ <code>NORTH</code> and <code>SOUTH</code> but may use ordinary
+ integer values {0, 1, 2, 3} as well. This imposes the
+ following problems:</para>
+
+ <glossentry>
+ <glossterm>Code Readability</glossterm>
+
+ <glossdef>
+ <para>A statement like <code>setDirection(2)</code> will
+ be more difficult to understand than its counterpart
+ <code>setDirection(NORTH)</code>. Currently we cannot
+ enforce the second way of coding.</para>
+ </glossdef>
+ </glossentry>
+
+ <glossentry>
+ <glossterm>Possible programming errors</glossterm>
+
+ <glossdef>
+ <para>A programmer may be misled to use illegal
+ directional values. Keeping a wrong set of directions in
+ mind e.g {1, 2, 3, 4} rather than {0, 1, 2, 3} will result
+ in errors. These may be hard to trace </para>
+ </glossdef>
+ </glossentry>
+ </glosslist>
+ </answer>
+ </qandaentry>
+ </qandadiv>
</qandaset>
</section>
--
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