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<?php
/**
* function for addition challenges
*/
function _math_captcha_addition_challenge() {
$argmax = intval(variable_get('math_captcha_addition_argmax', 10));
if (variable_get('math_captcha_addition_allow_negative', FALSE)) {
$x = mt_rand(-$argmax, $argmax);
$y = mt_rand(-$argmax, $argmax);
}
else {
$x = mt_rand(0, $argmax);
$y = mt_rand(0, $argmax);
}
$solution = $x + $y;
$maxlength = strlen(strval($argmax + $argmax)) + intval(variable_get('math_captcha_addition_allow_negative', FALSE));
return _math_captcha_build_captcha($x, $y, '+', $solution, $maxlength);
}
/**
* function for subtraction challenges
*/
function _math_captcha_subtraction_challenge() {
$argmax = intval(variable_get('math_captcha_subtraction_argmax', 10));
if (variable_get('math_captcha_subtraction_allow_negative', FALSE)) {
$x = mt_rand(-$argmax, $argmax);
$y = mt_rand(-$argmax, $argmax);
}
else {
$y = mt_rand(0, $argmax);
$x = mt_rand($y, $argmax);
}
$solution = $x - $y;
$maxlength = strlen(strval($argmax + $argmax)) + intval(variable_get('math_captcha_subtraction_allow_negative', FALSE));
return _math_captcha_build_captcha($x, $y, '-', $solution, $maxlength);
}
/**
* function for multiplication challenges
*/
function _math_captcha_multiplication_challenge() {
$argmax = intval(variable_get('math_captcha_multiplication_argmax', 5));
$x = mt_rand(1, $argmax);
$y = mt_rand(1, $argmax);
if (variable_get('math_captcha_multiplication_allow_negative', FALSE)) {
$x = $x * (mt_rand(0, 1) * 2 - 1);
$y = $y * (mt_rand(0, 1) * 2 - 1);
}
$solution = $x * $y;
$maxlength = strlen(strval($argmax * $argmax)) + intval(variable_get('math_captcha_multiplication_allow_negative', FALSE));
return _math_captcha_build_captcha($x, $y, '*', $solution, $maxlength);
}
/**
* helper function to build a math CAPTCHA form item
*/
function _math_captcha_build_captcha($x, $y, $operator, $result, $maxlength=3) {
$form_item = array();
$form_item['form']['captcha_response'] = array(
'#type' => 'textfield',
'#title' => t('Math question'),
'#required' => TRUE,
'#size' => $maxlength + 2,
'#maxlength' => $maxlength,
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'#description' => t('Solve this math question and enter the solution with digits. E.g. for "two plus four = ?" enter "6".'),
);
switch (mt_rand(0, 2)) {
case 0: // question like "x + y = ?"
$form_item['solution'] = "$result";
$form_item['form']['captcha_response']['#field_prefix'] = _math_captcha_repr($x, TRUE) .' '. _math_captcha_repr_op($operator) .' '. _math_captcha_repr($y, TRUE) .' '. _math_captcha_repr_op('=');
break;
case 1: // question like "x + ? = z"
$form_item['solution'] = "$y";
$form_item['form']['captcha_response']['#field_prefix'] = _math_captcha_repr($x, TRUE) .' '. _math_captcha_repr_op($operator) .' ';
$form_item['form']['captcha_response']['#field_suffix'] = ' '. _math_captcha_repr_op('=') .' '. _math_captcha_repr($result);
break;
case 2: // question like "? + y = z"
$form_item['solution'] = "$x";
$form_item['form']['captcha_response']['#field_suffix'] = ' '. _math_captcha_repr_op($operator) .' '. _math_captcha_repr($y, TRUE) .' '. _math_captcha_repr_op('=') .' '. _math_captcha_repr($result);
break;
}
return $form_item;
}
/**
* Helper function for transforming a number to a textual representation
*/
function _math_captcha_repr($n, $add_paratheses_when_negative=FALSE) {
// start with no textual representation
$t = "$n";
// if enabled and available: do textual representation
if (variable_get('math_captcha_textual_numbers', TRUE)) {
$repr_map = array(
0 => t('zero'), 1 => t('one'), 2 => t('two'), 3 => t('three'),
4 => t('four'), 5 => t('five'), 6 => t('six'), 7 => t('seven'), 8 => t('eight'),
9 => t('nine'), 10 => t('ten'), 11 => t('eleven'), 12 => t('twelve'),
13 => t('thirteen'), 14 => t('fourteen'), 15 => t('fifteen'),
);
if (array_key_exists(abs($n), $repr_map)) {
$t = $repr_map[abs($n)];
if ($n < 0) {
$t = t('minus !number', array('!number' => $t));
}
}
}
if ($add_paratheses_when_negative && $n < 0) {
$t = "($t)";
}
return $t;
}
function _math_captcha_repr_op($op) {
// start with no textual representation
$t = "$op";
// if enabled and available: do textual representation
if (variable_get('math_captcha_textual_operators', FALSE)) {
$repr_map = array('+' => t('plus'), '-' => t('minus'), '*' => t('times'), '=' => t('equals'));
if (array_key_exists($op, $repr_map)) {
$t = $repr_map[$op];
}
}
return $t;
}