function qformat_webct_convert_formula in Quiz 6.5

Same name and namespace in other branches

1. 6.6 includes/moodle/question/format/webct/format.php \qformat_webct_convert_formula()

1 call to qformat_webct_convert_formula()

qformat_webct::readquestions in includes/moodle/question/format/webct/format.php

Parses an array of lines into an array of questions, where each item is a question object as defined by readquestion(). Questions are defined as anything between blank lines.

File

includes/moodle/question/format/webct/format.php, line 67

Code

function qformat_webct_convert_formula($formula) {

  // Remove empty space, as it would cause problems otherwise:
  $formula = str_replace(' ', '', $formula);

  // Remove paranthesis after e,E and *10**:
  while (ereg('[0-9.](e|E|\\*10\\*\\*)\\([+-]?[0-9]+\\)', $formula, $regs)) {
    $formula = str_replace($regs[0], ereg_replace('[)(]', '', $regs[0]), $formula);
  }

  // Replace *10** with e where possible
  while (ereg('(^[+-]?|[^eE][+-]|[^0-9eE+-])[0-9.]+\\*10\\*\\*[+-]?[0-9]+([^0-9.eE]|$)', $formula, $regs)) {
    $formula = str_replace($regs[0], str_replace('*10**', 'e', $regs[0]), $formula);
  }

  // Replace other 10** with 1e where possible
  while (ereg('(^|[^0-9.eE])10\\*\\*[+-]?[0-9]+([^0-9.eE]|$)', $formula, $regs)) {
    $formula = str_replace($regs[0], str_replace('10**', '1e', $regs[0]), $formula);
  }

  // Replace all other base**exp with the PHP equivalent function pow(base,exp)
  // (Pretty tricky to exchange an operator with a function)
  while (2 == count($splits = explode('**', $formula, 2))) {

    // Find $base
    if (ereg('^(.*[^0-9.eE])?(([0-9]+(\\.[0-9]*)?|\\.[0-9]+)([eE][+-]?[0-9]+)?|\\{[^}]*\\})$', $splits[0], $regs)) {

      // The simple cases
      $base = $regs[2];
      $splits[0] = $regs[1];
    }
    else {
      if (ereg('\\)$', $splits[0])) {

        // Find the start of this parenthesis
        $deep = 1;
        for ($i = 1; $deep; ++$i) {
          if (!ereg('^(.*[^[:alnum:]_])?([[:alnum:]_]*([)(])([^)(]*[)(]){' . $i . '})$', $splits[0], $regs)) {
            error("Parenthesis before ** is not properly started in {$splits[0]}**");
          }
          if ('(' == $regs[3]) {
            --$deep;
          }
          else {
            if (')' == $regs[3]) {
              ++$deep;
            }
            else {
              error("Impossible character {$regs[3]} detected as parenthesis character");
            }
          }
        }
        $base = $regs[2];
        $splits[0] = $regs[1];
      }
      else {
        error("Bad base before **: {$splits[0]}**");
      }
    }

    // Find $exp (similar to above but a little easier)
    if (ereg('^([+-]?(\\{[^}]\\}|([0-9]+(\\.[0-9]*)?|\\.[0-9]+)([eE][+-]?[0-9]+)?))(.*)', $splits[1], $regs)) {

      // The simple case
      $exp = $regs[1];
      $splits[1] = $regs[6];
    }
    else {
      if (ereg('^[+-]?[[:alnum:]_]*\\(', $splits[1])) {

        // Find the end of the parenthesis
        $deep = 1;
        for ($i = 1; $deep; ++$i) {
          if (!ereg('^([+-]?[[:alnum:]_]*([)(][^)(]*){' . $i . '}([)(]))(.*)', $splits[1], $regs)) {
            error("Parenthesis after ** is not properly closed in **{$splits[1]}");
          }
          if (')' == $regs[3]) {
            --$deep;
          }
          else {
            if ('(' == $regs[3]) {
              ++$deep;
            }
            else {
              error("Impossible character {$regs[3]} detected as parenthesis character");
            }
          }
        }
        $exp = $regs[1];
        $splits[1] = $regs[4];
      }
    }

    // Replace it!
    $formula = "{$splits[0]}pow({$base},{$exp}){$splits[1]}";
  }

  // Nothing more is known to need to be converted
  return $formula;
}