lib/mathslib.php

   1 <?php
   2
   3 require_once $CFG->dirroot.'/lib/evalmath/evalmath.class.php';
   4
   5 /**
   6  * This class abstracts evaluation of spreadsheet formulas.
   7  * See unit tests in lib/simpletest/testmathslib.php for sample usage.
   8  *
   9  * @author Petr Skoda (skodak)
  10  * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
  11  */
  12 class calc_formula {
  13
  14     // private properties
  15     var $_em;
  16     var $_nfx   = false;   // postfix notation
  17     var $_error = false; // last error
  18
  19     /**
  20      * Constructor for spreadsheet formula with optional parameters
  21      *
  22      * @param string $formula with leading =
  23      * @param array $params associative array of parameters used in formula. All parameter names must be lowercase!
  24      */
  25     function calc_formula($formula, $params=false) {
  26         $this->_em = new EvalMath();
  27         $this->_em->suppress_errors = true;
  28         if (strpos($formula, '=') !== 0) {
  29             $this->_error = "missing leading '='";
  30             return;
  31         }
  32         $formula = substr($formula, 1);
  33         if (strpos($formula, '=') !== false) {
  34             $this->_error = "too many '='";
  35             return;
  36         }
  37         $this->_nfx = $this->_em->nfx($formula);
  38         if ($this->_nfx == false) {
  39             $this->_error = $this->_em->last_error;
  40             return;
  41         }
  42         if ($params != false) {
  43             $this->set_params($params);
  44         }
  45     }
  46
  47     /**
  48      * Raplace parameters used in existing formula,
  49      * parameter names must contain only lowercase [a-z] letters, no other characters are allowed!
  50      *
  51      * @param array $params associative array of parameters used in formula
  52      */
  53     function set_params($params) {
  54         $this->_em->v = $params;
  55     }
  56
  57     /**
  58      * Evaluate formula
  59      *
  60      * @return mixed number if ok, false if error
  61      */
  62     function evaluate() {
  63         if ($this->_nfx == false) {
  64             return false;
  65         }
  66         $res = $this->_em->pfx($this->_nfx);
  67         if ($res === false) {
  68             $this->_error = $this->_em->last_error;
  69             return false;
  70         } else {
  71             $this->_error = false;
  72             return $res;
  73         }
  74     }
  75
  76     /**
  77      * Get last error.
  78      * TODO: localize the strings from contructor and EvalMath library
  79      *
  80      * @return mixed string with last error description or false if ok
  81      */
  82     function get_error() {
  83         return $this->_error;
  84     }
  85 }
  86
  87 ?>