lib/mathslib.php

   1 <?php
   2
   3 // This file is part of Moodle - http://moodle.org/
   4 //
   5 // Moodle is free software: you can redistribute it and/or modify
   6 // it under the terms of the GNU General Public License as published by
   7 // the Free Software Foundation, either version 3 of the License, or
   8 // (at your option) any later version.
   9 //
  10 // Moodle is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 // GNU General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU General Public License
  16 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  17
  18 /**
  19  * @package    core
  20  * @subpackage lib
  21  * @copyright  Petr Skoda (skodak)
  22  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23  */
  24
  25 defined('MOODLE_INTERNAL') || die();
  26
  27 /** @see evalmath/evalmath.class.php */
  28 require_once $CFG->dirroot.'/lib/evalmath/evalmath.class.php';
  29
  30 /**
  31  * This class abstracts evaluation of spreadsheet formulas.
  32  * See unit tests in lib/tests/mathslib_test.php for sample usage.
  33  *
  34  * @package moodlecore
  35  * @copyright Petr Skoda (skodak)
  36   * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  37  */
  38 class calc_formula {
  39
  40     // private properties
  41     var $_em;
  42     var $_nfx   = false;   // postfix notation
  43     var $_error = false; // last error
  44
  45     /**
  46      * Constructor for spreadsheet formula with optional parameters
  47      *
  48      * @param string $formula with leading =
  49      * @param array $params associative array of parameters used in formula. All parameter names must be lowercase!
  50      */
  51     function calc_formula($formula, $params=false) {
  52         $this->_em = new EvalMath();
  53         $this->_em->suppress_errors = true; // no PHP errors!
  54         if (strpos($formula, '=') !== 0) {
  55             $this->_error = "missing leading '='";
  56             return;
  57         }
  58         $formula = substr($formula, 1);
  59         if (strpos($formula, '=') !== false) {
  60             $this->_error = "too many '='";
  61             return;
  62         }
  63         $this->_nfx = $this->_em->nfx($formula);
  64         if ($this->_nfx == false) {
  65             $this->_error = $this->_em->last_error;
  66             return;
  67         }
  68         if ($params != false) {
  69             $this->set_params($params);
  70         }
  71     }
  72
  73     /**
  74      * Raplace parameters used in existing formula,
  75      * parameter names must contain only lowercase [a-z] letters, no other characters are allowed!
  76      *
  77      * @param array $params associative array of parameters used in formula
  78      */
  79     function set_params($params) {
  80         $this->_em->v = $params;
  81     }
  82
  83     /**
  84      * Evaluate formula
  85      *
  86      * @return mixed number if ok, false if error
  87      */
  88     function evaluate() {
  89         if ($this->_nfx == false) {
  90             return false;
  91         }
  92         $res = $this->_em->pfx($this->_nfx);
  93         if ($res === false) {
  94             $this->_error = $this->_em->last_error;
  95             return false;
  96         } else {
  97             $this->_error = false;
  98             return $res;
  99         }
 100     }
 101
 102     /**
 103      * Get last error.
 104      * TODO: localize the strings from contructor and EvalMath library
 105      *
 106      * @return mixed string with last error description or false if ok
 107      */
 108     function get_error() {
 109         return $this->_error;
 110     }
 111
 112     /**
 113      * Similar to format_float, formats the numbers and list separators
 114      * according to locale specifics.
 115      * @param string $formula
 116      * @return string localised formula
 117      */
 118     public static function localize($formula) {
 119         $formula = str_replace('.', '$', $formula); // temp placeholder
 120         $formula = str_replace(',', get_string('listsep', 'langconfig'), $formula);
 121         $formula = str_replace('$', get_string('decsep', 'langconfig'), $formula);
 122         return $formula;
 123     }
 124
 125     /**
 126      * Similar to unformat_float, converts floats and lists to PHP standards.
 127      * @param string $formula localised formula
 128      * @return string
 129      */
 130     public static function unlocalize($formula) {
 131         $formula = str_replace(get_string('decsep', 'langconfig'), '$', $formula);
 132         $formula = str_replace(get_string('listsep', 'langconfig'), ',', $formula);
 133         $formula = str_replace('$', '.', $formula); // temp placeholder
 134         return $formula;
 135     }
 136 }