Merge branch 'master' into issue_289_comment

Author: habibasorour

source/ch3_javadatatypes.ptx

@@ -729,36 +729,54 @@ public class Histo {
         </p>
 
         <p>
- The syntax of this for loop probably looks very strange to you, but in fact it is not too different from what happens in Python using range. In fact <c>for (Integer i = 0; i &lt; 10; i++)</c> is exactly equivalent to the Python <c>for i in range(10)</c> The first statement inside the parenthesis declares and initializes a loop variable <c>i</c>. The second statement is a Boolean expression that is our exit condition. In other words we will keep looping as long as this expression evaluates to true. The third clause is used to increment the value of the loop variable at the end of iteration through the loop. In fact <c>i++</c> is Java shorthand for <c>i = i + 1</c> Java also supports the shorthand <c>i--</c> to decrement the value of i. Like Python, you can also write <c>i += 2</c> as shorthand for <c>i = i + 2</c> Try to rewrite the following Python for loops as Java for loops: 
-        </p>
-
-        <p>
-            <ul>
-                <li>
-                    <p>
-                        <c>for i in range(2,101,2)</c>
-                    </p>
-                </li>
+ The syntax of this for loop probably looks very strange to you, but in fact it is not too different from what happens in Python using range. In fact <c>for (Integer i = 0; i &lt; 10; i++)</c> is exactly equivalent to the Python <c>for i in range(10)</c> The first statement inside the parenthesis declares and initializes a loop variable <c>i</c>. The second statement is a Boolean expression that is our exit condition. In other words we will keep looping as long as this expression evaluates to true. The third clause is used to increment the value of the loop variable at the end of iteration through the loop. In fact <c>i++</c> is Java shorthand for <c>i = i + 1</c> Java also supports the shorthand <c>i--</c> to decrement the value of i. Like Python, you can also write <c>i += 2</c> as shorthand for <c>i = i + 2</c>. </p>
 
-                <li>
-                    <p>
-                        <c>for i in range(1,100)</c>
-                    </p>
-                </li>
-
-                <li>
-                    <p>
-                        <c>for i in range(100,0,-1)</c>
-                    </p>
-                </li>
-
-                <li>
-                    <p>
-                        <c>for x,y in zip(range(10),range(0,20,2))</c> [hint, you can separate statements in the same clause with a ,]
-                    </p>
-                </li>
-            </ul>
-        </p>
+<exercise label="matching-python-java-loops">
+  <statement>
+    <p>
+      Match each Python <c>for</c> loop with its equivalent Java <c>for</c> loop. 
+    </p>
+  </statement>
+     
+  <matches>
+
+    <match>
+      <premise><c>for i in range(2, 102, 2)</c></premise>
+      <response><c>for (int i = 2; i &lt; 102; i += 2)</c></response>
+    </match>
+
+    <match>
+      <premise><c>for i in range(1, 100)</c></premise>
+      <response><c>for (int i = 1; i &lt; 100; i++)</c></response>
+    </match>
+
+     <match>
+      <response><c>for (int i = 1; i &lt;= 100; i++)</c></response>
+    </match>
+
+    <match>
+      <premise><c>for i in range(100, 0, -1)</c></premise>
+      <response><c>for (int i = 100; i &gt; 0; i--)</c></response>
+    </match>
+    
+    <match>
+      <response><c>for (int i = 2; i &lt;= 102; i += 2)</c></response>
+    </match>
+
+     <match>
+      <premise><c>for x, y in zip(range(10), range(0, 20, 2))</c></premise>
+      <response><c>for (int x = 0, y = 0; x &lt; 10; x++, y += 2)</c></response>
+    </match> 
+   
+    <match>
+      <response><c>for (int i = 100; i &lt; 0; i--)</c></response>
+    </match>
+
+    <match>
+      <response><c>for (int x = 0, int y = 0; x &lt; 10; x++, y += 2)</c></response>
+    </match>
+  </matches>
+</exercise>
 
         <p>
  The next loop (lines 27&#x2013;30) shows a typical Java pattern for reading data from a file. Java while loops and Python while loops are identical in their logic. In this case, we will continue to process the body of the loop as long as <c>data.hasNextInt()</c> returns true. 

source/ch5_loopsanditeration.ptx

@@ -17,7 +17,7 @@
 
         <program  xml:id="python-definite-loop"  interactive="activecode" language="python">
             <code>
-for i in range(10):
+for i in range(10): # range(10) is a list of integers from 0 to 9
     print(i)
             </code>
         </program>
@@ -30,7 +30,7 @@ for i in range(10):
             <code>
 public class DefiniteLoopExample {
     public static void main(String[] args) {
-        for (Integer i = 0; i &lt; 10; i++ ) {
+        for (Integer i = 0; i &lt; 10; i++ ) { // notice how the initialization, condition, and update are all on the same line.
             System.out.println(i);
         }
     }
@@ -67,7 +67,7 @@ public class DefiniteLoopExample {
 
         <program xml:id="python-deinite-decrement" interactive="activecode" language="python">
             <code>
-for i in range(100, -1, -5):
+for i in range(100, -1, -5): # start at 100, stop at 0, decrement by 5
     print(i)
             </code>
         </program>
@@ -80,7 +80,7 @@ for i in range(100, -1, -5):
             <code>
 public class DefiniteLoopBackward {
     public static void main(String[] args) {
-        for (Integer i = 100; i &gt;= 0; i -= 5) {
+        for (Integer i = 100; i &gt;= 0; i -= 5) { // start at 100, stop at 0, decrement by 5
             System.out.println(i);
         }
     }
@@ -99,8 +99,8 @@ public class DefiniteLoopBackward {
 
         <program  xml:id="python-list-iteration" interactive="activecode" language="python">
             <code>
-l = [1, 1, 2, 3, 5, 8, 13, 21]
-for fib in l:
+l = [1, 1, 2, 3, 5, 8, 13, 21] # create a list of integers
+for fib in l: # iterate over the list
     print(fib)
             </code>
         </program>
@@ -115,16 +115,16 @@ import java.util.ArrayList;
 
 public class ForEachArrayListExample {
     public static void main(String[] args) {
-        ArrayList&lt;Integer&gt; l = new ArrayList&lt;Integer&gt;();
-        l.add(1);
-        l.add(1);
-        l.add(2);
+        ArrayList&lt;Integer&gt; l = new ArrayList&lt; // create an ArrayList of integers
+        l.add(1); // add the first integer to the list
+        l.add(1); // add the second integer to the list
+        l.add(2); // keep going
         l.add(3);
         l.add(5);
         l.add(8);
         l.add(13);
-        l.add(21);
-        for (Integer i : l) {
+        l.add(21); // add the last integer to the list
+        for (Integer i : l) { // iterate over the list
             System.out.println(i);
         }
     }
@@ -141,8 +141,8 @@ public class ForEachArrayListExample {
             <code>
 public class ForEachArrayExample {
     public static void main(String[] args) {
-        int l[] = {1,1,2,3,5,8,13,21};
-        for(int i : l) {
+        int l[] = {1,1,2,3,5,8,13,21}; // create an array of integers using primitive syntax
+        for(int i : l) { // iterate over the array
             System.out.println(i);
         }
     }
@@ -158,8 +158,8 @@ public class ForEachArrayExample {
             <code>
 public class StringIterationExample {
     public static void main(String[] args) {
-        String t = "Hello World";
-        for (char c : t.toCharArray()) {
+        String t = "Hello World"; // create a string
+        for (char c : t.toCharArray()) { // iterate over the characters in the string
             System.out.println(c);
         }
     }
@@ -181,7 +181,7 @@ public class StringIterationExample {
 i = 5
 while i &gt; 0: # while i is greater than 0
     print(i)
-    i = i - 1 # decrement i by 1
+    i = i - 1 
             </code>
         </program>
 
@@ -214,7 +214,7 @@ public class WhileLoopExample {
             <code>
 public class DoWhileExample {
     public static void main(String[] args) {
-        int i = 10; // initialize i to 10
+        int i = 10; 
         do { // do-while loop, will run at least once no matter the condition
             System.out.println("This runs once, i = " + i);
         } while (i &lt; 5); // while i is less than 5