16   if (!is_null($hc1->constant)) { return $hc1; };
20   if (!is_null($hc2->constant)) { return $hc2; };
47   var $constant;  variable in HCConstraint
52     if (!is_null($this->constant)) { 
53       return $this->applicable_value($this->constant, $box); 
113           is_null($box->parent->_height_constraint->constant) &&
141       $constant = null;
143       $constant = array($value->getPercentage(), true);
145       $constant = array($value->getPoints(), false);
168     $constraint =& new HCConstraint($constant, $min, $max);
178   function HCConstraint($constant, $min, $max) {  argument
179     $this->constant = $constant;
201     if (!is_null($this->constant)) {
202       $height = $this->_fix_value($this->constant, $box, $value, $no_table_recursion);
227       is_null($this->constant);