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87 lines
2.4 KiB
PHP
87 lines
2.4 KiB
PHP
<?php
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require_once $CFG->dirroot.'/lib/evalmath/evalmath.class.php';
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/**
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* This class abstracts evaluation of spreadsheet formulas.
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* See unit tests in lib/simpletest/testmathslib.php for sample usage.
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*
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* @author Petr Skoda (skodak)
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* @license http://www.gnu.org/copyleft/gpl.html GNU Public License
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*/
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class calc_formula {
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// private properties
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var $_em;
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var $_nfx = false; // postfix notation
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var $_error = false; // last error
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/**
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* Constructor for spreadsheet formula with optional parameters
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*
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* @param string $formula with leading =
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* @param array $params associative array of parameters used in formula. All parameter names must be lowercase!
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*/
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function calc_formula($formula, $params=false) {
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$this->_em = new EvalMath();
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$this->_em->suppress_errors = true;
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if (strpos($formula, '=') !== 0) {
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$this->_error = "missing leading '='";
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return;
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}
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$formula = substr($formula, 1);
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if (strpos($formula, '=') !== false) {
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$this->_error = "too many '='";
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return;
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}
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$this->_nfx = $this->_em->nfx($formula);
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if ($this->_nfx == false) {
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$this->_error = $this->_em->last_error;
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return;
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}
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if ($params != false) {
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$this->set_params($params);
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}
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}
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/**
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* Raplace parameters used in existing formula,
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* parameter names must contain only lowercase [a-z] letters, no other characters are allowed!
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*
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* @param array $params associative array of parameters used in formula
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*/
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function set_params($params) {
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$this->_em->v = $params;
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}
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/**
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* Evaluate formula
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*
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* @return mixed number if ok, false if error
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*/
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function evaluate() {
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if ($this->_nfx == false) {
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return false;
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}
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$res = $this->_em->pfx($this->_nfx);
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if ($res === false) {
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$this->_error = $this->_em->last_error;
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return false;
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} else {
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$this->_error = false;
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return $res;
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}
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}
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/**
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* Get last error.
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* TODO: localize the strings from contructor and EvalMath library
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*
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* @return mixed string with last error description or false if ok
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*/
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function get_error() {
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return $this->_error;
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}
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}
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?>
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