PHP Algorithm for Inverse Polish expressions-dedicated for wage calculation

A netizen wrote to me about the salary calculation in PHP. In my previous article, I talked about a method to calculate wages, but it was just a coincidence that I used an existing expression tool. Now, if someone wants it, I will give an algorithm against Poland.

Our goal is to implement the following formula:

Assume that there is a formula as follows:

$expression = "(F1*F12+10.34)";

The variable values are as follows:

$expression_value = Array('F1'=>10,'F12'=>20);

We hope to use PHP to construct a class to calculate the value of this expression. This kind of application is mainly used in web wage management, where users can customize their wage phase formulas.

$ Rpn = new Math_Rpn (); $ Rpn-> setExpressionValue ($ expression_value ); Echo $ rpn-> calculate ($ expression, 'deg ', false); // It is the corresponding value.

The method for parsing the inverse polish expression. In the compilation principle, the expression is first decomposed into a symbol array, then the inverse Polish formula is obtained, and the result is obtained according to the inverse Polish formula.

I put the three functions below respectively. In essence, I Hack the RPN function of Pear.

function _stringToArray () { $temp_operator = null; $temp_value = null; $this->_input = str_replace(" ","",$this->_input); for($i = 0; $i < strlen($this->_input); $i++) { if ($this->_input[$i] == ' ') {   if ($temp_operator != null) { array_push($this->_input_array, $temp_operator); $temp_operator = null;   }   if ($temp_value != null) { array_push($this->_input_array, $temp_value); $temp_value = null;   } } elseif (($temp_value == null) && $temp_operator != ')' && (!array_key_exists($temp_operator,$this->_operation) || !array_key_exists(2,$this->_operation[$temp_operator]) || $this->_operation[$temp_operator][2]>0) && ($this->_input[$i] == '-')) {   if ($temp_operator != null) { array_push($this->_input_array, $temp_operator); $temp_operator = null;   }   array_push($this->_input_array, '-1');   array_push($this->_input_array, '*'); //} elseif ((is_numeric($this->_input[$i])) || ($this->_input[$i] == '.')) { } elseif ((is_numeric($this->_input[$i])) || ($this->_input[$i] == '.') || ($this->_input[$i] == 'F')) {   if ($temp_operator != null) { array_push($this->_input_array, $temp_operator); $temp_operator = null;   }   $temp_value .= $this->_input[$i]; } else {   if ($this->_keyExists($temp_operator, $this->_operation, 1)) { array_push($this->_input_array, $temp_operator); $temp_operator = null;   }   if ($temp_value != null) { array_push($this->_input_array, $temp_value); $temp_value = null;   }   $temp_operator .= $this->_input[$i]; } } if ($temp_operator != null && $temp_operator != ' ') { array_push($this->_input_array, $temp_operator); } elseif($temp_value != null && $temp_value != ' ') { array_push($this->_input_array, $temp_value); } // $this->_testInput(); print_r($this->_expression_value); print_r($this->_input_array); return $this->_input_array;   }   function _arrayToRpn() { if ($this->_error <> null) { $this->_output = array(); return $this->_output; } for($i = 0; $i < count($this->_input_array); $i++) { $temp = $this->_input_array[$i]; if (is_numeric($temp)) {   $this->_outputAdd($temp); } else if($this->_keyExists($temp, $this->_expression_value, 0)) {   $this->_outputAdd($this->_expression_value[$temp]); } else {   if ($temp == ')') { while(!$this->_stackEmpty() && ($this->_stackPriority() >= 1)) { $this->_outputAdd($this->_stackDelete()); } if (!$this->_stackEmpty()) { $this->_stackDelete(); }   } elseif ($temp=='(') { $this->_stackAdd($temp);   } elseif (($this->_stackEmpty()) || (($this->_priority($temp) > $this->_stackPriority()))) { $this-> _stackAdd($temp);   } else { while(!$this->_stackEmpty() && ($this->_priority($temp) <= $this->_stackPriority())) { $this->_outputAdd($this->_stackDelete()); } $this->_stackAdd($temp);   } } } while(!$this->_stackEmpty()) { $this->_outputAdd($this->_stackDelete()); } return $this->_output; } function _rpnToValue() { $time1 = $this->_getMicroTime(); if ($this->_error <> null) { $this->_value = null; return $this->_value; } $this->_value = 0; $temp = $this->_output; do { $pos = $this->_nextOperator($temp); if ($pos == -1) {   $this->_error = $this->_raiseError('Syntax error');   $this->_value = null;   return $this->_value; } $operator = $this->_operation[$temp[$pos]]; $arg = $operator[2]; $function = $operator[3]; if (($arg==2) && (!isset($temp[$pos-1]) || !is_numeric($temp[$pos-1]) || !isset($temp[$pos-2]) || !is_numeric($temp[$pos-2]))) {   $this->_error = $this->_raiseError('Syntax error');   $this->_value = null;   return $this->_value; } elseif (($arg==1) && (!isset($temp[$pos-1]) || !is_numeric($temp[$pos-1]))) {   $this->_error = $this->_raiseError('Syntax error');   $this->_value = null;   return $this->_value; } if(is_array($function)) {   if($arg==2) $arg_array = array($temp[$pos-2],$temp[$pos-1]);   elseif($arg==1) $arg_array = array($temp[$pos-1]);   else $arg_array = array();   if($function['type'] == 'userFunction') { $this->_value = call_user_func_array($function['function'], $arg_array);   } else { $function_array = array(&$function['class'], $function['method']); $this->_value = call_user_func_array($function_array, $arg_array);   } } else {   $this->_value = $this->$function($temp, $pos); } if ($this->_isNan($this->_value)) {   $this->_error = $this->_raiseError('NAN value');   $this->_value = null;   return $this->_value; } elseif ($this->_isInfinite($this->_value)) {   $this->_error = $this->_raiseError('Infinite value');   $this->_value = null;   return $this->_value; } elseif (is_null($this->_value)) {   return $this->_value; } $temp = $this->_refresh($temp, $pos, $arg, $this->_value); } while(count($temp) > 1); $this->_value = $temp[0]; $time2 = $this->_getMicroTime(); $this->_timer = $time2 - $time1; return $this->_value;   }