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* @copyright 1999 onwards Martin Dougiamas {@link http://moodle.com}
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* @copyright 1999 onwards Martin Dougiamas {@link http://moodle.com}
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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*/
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class qtype_calculated extends question_type {
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class qtype_calculated extends question_type {
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/**
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/**
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* @var string a placeholder is a letter, followed by almost any characters. (This should probably be restricted more.)
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* @var string a placeholder is a letter, followed by zero or more alphanum chars (as well as space, - and _ for readability).
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*/
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*/
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const PLACEHOLDER_REGEX_PART = '[[:alpha:]][^>} <`{"\']*';
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const PLACEHOLDER_REGEX_PART = '[[:alpha:]][[:alpha:][:digit:]\-_\s]*';
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/**
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/**
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* @var string REGEXP for a placeholder, wrapped in its {...} delimiters, with capturing brackets around the name.
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* @var string REGEXP for a placeholder, wrapped in its {...} delimiters, with capturing brackets around the name.
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*/
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*/
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}
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}
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// Validates the formula submitted from the question edit page.
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// Validates the formula submitted from the question edit page.
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// Returns false if everything is alright
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// Returns false if everything is alright
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// otherwise it constructs an error message.
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// otherwise it constructs an error message.
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// Strip away dataset names. Use 1.0 to catch illegal concatenation like {a}{b}.
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// Strip away dataset names. Use 1.0 to remove valid names, so illegal names can be identified later.
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$formula = preg_replace(qtype_calculated::PLACEHODLER_REGEX, '1.0', $formula);
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$formula = preg_replace(qtype_calculated::PLACEHODLER_REGEX, '1.0', $formula);
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// Strip away empty space and lowercase it.
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$formula = strtolower(str_replace(' ', '', $formula));
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// Strip away empty space and lowercase it.
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$formula = strtolower(str_replace(' ', '', $formula));
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// Only mathematical operators are supported. Bitwise operators are not safe.
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// Note: In this context, ^ is a bitwise operator (exponents are represented by **).
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$safeoperatorchar = '-+/*%>:\~<?=!';
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$safeoperatorchar = '-+/*%>:^\~<?=&|!'; /* */
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$operatorornumber = "[{$safeoperatorchar}.0-9eE]";
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$operatorornumber = "[{$safeoperatorchar}.0-9eE]";
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// Validate mathematical functions in formula.
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while (preg_match("~(^|[{$safeoperatorchar},(])([a-z0-9_]*)" .
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while (preg_match("~(^|[{$safeoperatorchar},(])([a-z0-9_]*)" .
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