Merge pull request #264 from habibasorour/issue_250_listing

Issue 250 fixed: Added listing to 4.2

Author: pearcej

source/ch4_conditionals.ptx

@@ -55,8 +55,9 @@ if score >= 90: # Note the colon at the end of the line
     <section xml:id="use-the-if-else-statement">
         <title>Using the <c>if</c> - <c>else</c> Statement</title>
 
-            <p>The Java equivalent follows the same syntactical rules as before.</p>
-        <program xml:id="python-if-else" interactive="activecode" language="python">
+        <p><xref ref= "python-if-else"  text="type-global"/> shows how the <c>if</c> - <c>else</c>statement is written in Python.</p> 
+        <listing xml:id="python-if-else">
+        <program interactive="activecode" language="python">
             <code>
             age = 16
             if age &gt;= 18:
@@ -65,8 +66,11 @@ if score &gt;= 90: # Note the colon at the end of the line
                 print("You are not yet eligible to vote.")
             </code>
             </program>
-
-        <program xml:id="java-if-else" language="java">
+            </listing> 
+        
+        <p> <xref ref="java-if-else" text="type-global"/> is Java equivalent that follows the same syntactical rules as before.</p>
+        <listing xml:id="java-if-else">
+        <program interactive="activecode" language="java">
             <code>
         public class IfElseExample {
             public static void main(String[] args) {
@@ -80,6 +84,7 @@ if score &gt;= 90: # Note the colon at the end of the line
         }
             </code>
         </program>
+        </listing>
     </section>
 
     <section xml:id="elif">