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Commit 5cf12a9f authored by Goik Martin's avatar Goik Martin
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Cosmetics

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Doc/Sd1/Exam/2020/Summer/exam.xml
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......@@ -190,8 +190,9 @@ Provided: double</screen>
</listitem>
<listitem>
<para>The cleanest way is replacing the <code>double</code>
literal by a a <code>float</code> literal:</para>
<para>Replacing the <code>double</code> literal by a a
<code>float</code> literal leaves us with an overall
<code>float</code> expression resolving the issue:</para>
<screen>radius * radius * 3.1415926<emphasis role="red">F</emphasis>
......@@ -200,8 +201,6 @@ Provided: double</screen>
int * float
⭨ ⭩
float</screen>
<para>This resolves the return type clash.</para>
</listitem>
</orderedlist>
</answer>
......@@ -229,14 +228,14 @@ Provided: double</screen>
adds a logging statement:</para>
<programlisting language="java">static public int getSquare (int value) {
int result = value * value;
final int result = value * value;
log.info(result);
return result;
}</programlisting>
<para>The team is baffled: Albeit squares of integer values are
expected to be always positive occasionally negative results show
up:</para>
expected to be strictly positive occasionally negative results
show up:</para>
<screen>INFO [main] sd1.SupportMethods (SupportMethods.java:15) - -1757895751</screen>
......@@ -289,9 +288,23 @@ Provided: double</screen>
</informaltable>
<para>The product <code>46341 * 46341</code> of type
<code>int</code> however exceeds this value for the very first
time. Due to an <code>int</code>'s four-byte two complement
representation we have:</para>
<code>int</code> for example exceeds <inlineequation>
<m:math display="inline">
<m:mrow>
<m:msup>
<m:mi>2</m:mi>
<m:mi>31</m:mi>
</m:msup>
<m:mo>-</m:mo>
<m:mi>1</m:mi>
</m:mrow>
</m:math>
</inlineequation> for the very first time. Due to an
<code>int</code>'s four-byte two complement representation we
have:</para>
<informaltable border="1">
<tr>
......@@ -306,12 +319,16 @@ Provided: double</screen>
<td valign="top"><screen>-2147479015</screen></td>
</tr>
</informaltable>
<para>Starting from <code>46341</code> all computed squares
are simply wrong due to arithmetic overflow regardless of
their result's sign. </para>
</listitem>
<listitem>
<para>Solving the issue requires a data type being able to
accommodate squares of arbitrary <code>int</code> values. The
smallest int value is <inlineequation>
<para>Solving the issue requires a data type to accommodate
squares of arbitrary <code>int</code> values. The smallest int
value (having maximum amount) is <inlineequation>
<m:math display="inline">
<m:mrow>
<m:mo>-</m:mo>
......@@ -323,7 +340,7 @@ Provided: double</screen>
</m:msup>
</m:mrow>
</m:math>
</inlineequation> and its square thus <inlineequation>
</inlineequation>. Its square is thus <inlineequation>
<m:math display="inline">
<m:msup>
<m:mi>2</m:mi>
......@@ -331,12 +348,31 @@ Provided: double</screen>
<m:mi>62</m:mi>
</m:msup>
</m:math>
</inlineequation>.We choose <code>long</code> as result
type. Turning an <code>int</code> into a long is easy:</para>
</listitem>
</inlineequation>. Choosing return type <code>long</code>
allows for a maximum value of <inlineequation>
<m:math display="inline">
<m:mrow>
<m:msup>
<m:mi>2</m:mi>
<listitem>
<para/>
<m:mi>63</m:mi>
</m:msup>
<m:mo>-</m:mo>
<m:mi>1</m:mi>
</m:mrow>
</m:math>
</inlineequation>which is ways larger than required. Turning
the <code>int</code> into a <code language="java">long</code>
expression is easy:</para>
<programlisting language="java">static public long getSquare (int value) {
long result = value;
result *= value;
log.info(result);
return result;
}</programlisting>
</listitem>
</orderedlist>
</answer>
......
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