for-loop

LAST UPDATED: 2008-07-03

Shortcuts: C C++ Java PHP Python Ruby

C:

/* Prints 0, 1, 2, ... 9 */
int i;
for (i = 0; i < 10; ++i) {
    printf("%d\n", i);
}

C++:

// Prints 0, 1, 2, ... 9
for (int i = 0; i < 10; ++i) {
    cout << i << endl;
}

Java:

// for-loop
// Prints 0, 1, 2, ... 9
for (int i = 0; i < 10; ++i) {
    System.out.println(i);
}

// foreach-loop (since Java 5.0)
// This works for arrays and classes that implement Iterable.
String[] a = {"Alpha", "Beta", "Gamma", "Delta"};
for (String elem : a) {
    System.out.println(elem);
}

PHP:

# for-loop (normal syntax)
for ($i = 0; $i < 10; ++$i) {
    echo $i, "\n";
}

# for-loop (alternate syntax)
for ($i = 0; $i < 10; ++$i):
    echo $i, "\n";
endfor;

# foreach-loop (since PHP 4)
# In PHP 4, this only works for arrays.
# In PHP 5, this also works for iterating objects.

# foreach-loop (normal syntax)
$a = array('Alpha', 'Beta', 'Gamma', 'Delta');
foreach ($a as $elem) {
    echo $elem, "\n";
}

# foreach-loop (alternate syntax)
$a = array('Alpha', 'Beta', 'Gamma', 'Delta');
foreach ($a as $elem):
    echo $elem, "\n";
endforeach;

# foreach-loop (normal syntax)
$a = array(
    'A' => 'Alpha',
    'B' => 'Beta',
    'C' => 'Gamma',
    'D' => 'Delta'
);
foreach ($a as $key => $value) {
    echo $key, "\t", $value, "\n";
}

# foreach-loop (alternate syntax)
$a = array(
    'A' => 'Alpha',
    'B' => 'Beta',
    'C' => 'Gamma',
    'D' => 'Delta'
);
foreach ($a as $key => $value):
    echo $key, "\t", $value, "\n";
endforeach;

Python:

# for-loop (with range(), ascending)
# Prints 0, 1, 2, ... 9
for i in range(10):
    print i

# for-loop (with range(), ascending)
# Prints 0, 1, 2, ... 9
for i in range(0, 10):
    print i

# for-loop (with range(), descending)
# Prints 10, 9, 8, ... 1
for i in range(10, 0, -1):
    print i

# foreach-loop
a = ['Alpha', 'Beta', 'Gamma', 'Delta']
for elem in a:
    print elem

Ruby:

# for-loop (inclusive range)
# Prints 0, 1, 2, ... 9
for i in 0..9 do
    puts i
end

# for-loop (exclusive range)
# Prints 0, 1, 2, ... 9
for i in 0...10 do
    puts i
end

# for-loop (with upto())
# Prints 0, 1, 2, ... 9
0.upto(9) do |i|
    puts i
end

# for-loop (with downto())
# Prints 10, 9, 8, ... 1
10.upto(1) do |i|
    puts i
end

# for-loop (brace style)
# Prints 10, 9, 8, ... 1
# "{}" style to write "do ... end"
10.upto(1) { |i|
    puts i
}