# Solutions to the exercises

<?php
/*
* Created on Feb 18, 2008
*
* Solutions to in-class exercises.
*
*/
?>
<HTML>
<HEAD>
<TITLE>Sum Example</TITLE>
</HEAD>
<BODY>
<H4>Computing a sum</h4>
<?php
// Initialize a sum to 0, then repeated add m, (m+1), ..., n to it.
function sum($m, $n) {
$sum = 0;
for ($k = 0; $k <= $n; $k++) {
$sum += $k;
}
return $sum;
}
$x = 1;
$y = 10;
echo "The sum of $x ... $y is " . sum($x, $y) . "<BR>";
echo "The sum of 10 ... 20 is " . sum(10, 20) . "<BR>";
// Initialze a product, then repeated multiply it by 1, 2, ..., $n
function factorial($n) {
$product = 1;
for ($k = 1; $k <= $n; $k++)
$product *= $k;
return $product;
}
// For CS Majors: A recursive factorial -- it calls itself instead of using a loop
function rFactorial($n) {
if ($n == 0)
return 1;
else
return $n * rFactorial($n-1);
}
echo "0! is " . factorial(0) . "<BR>";
echo "5! is " . factorial(5) . "<BR>";
echo "10! is " . factorial(10) . "<BR>";
// Go through each letter of the string comparing it to a blank.
// If it's blank, add 1 to the counter.
function countBlanks($str) {
$count = 0;
for ($k=0; $k < strlen($str); $k++)
if ($str[$k] == ' ')
++$count;
return $count;
}
echo "'hello world!' has " . countBlanks("hello world!") . " blanks<BR>";
echo "' hello world! this is a test ' has " . countBlanks(" hello world! this is a test ") . " blanks<BR>";
?>
</BODY>
</HTML>