Algorithm of PHP reverse Polish expression - special for salary calculation_PHP tutorial

A netizen wrote to me about the issue of salary calculation in PHP. I talked about a method of calculating wages in a previous article, but it was just a clever way to use existing expression tools. Now since someone wants it, I will give you a reverse Polish algorithm.

Our goal is to achieve the following calculation formula:

Suppose there is a calculation formula as follows:

<p>$expression = "(F1*F12+10.34)";</p>

The variable values ​​are as follows:

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

We want to build a class in PHP to calculate the value of this expression. This application is mainly used in web salary management, where users can customize their salary formulas.

<p>$rpn = new Math_Rpn();<br>$rpn->setExpressionValue($expression_value);  <br>echo $rpn->calculate($expression,'deg',false); // 即为相应的值</p>

The method of parsing the reverse Polish expression, which is included in the compilation principle, is to first decompose the expression into a symbolic array, then find the reverse Polish expression, and finally obtain it according to the reverse Polish expression as a result.

I posted the three functions below. In fact, I basically hacked Pear's RPN function.

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

 

http://www.bkjia.com/PHPjc/446823.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446823.htmlTechArticleA netizen wrote to me about the issue of salary calculation with PHP. I talked about a method of calculating wages in a previous article, but it was just a clever way to use existing expression tools. Now...