PHP Inverse Polish expression algorithm-dedicated _php tutorial for payroll calculation

A netizen wrote to me about the calculation of salary in PHP. I've talked about a method of calculating wages in a previous article, but Shang, using the tools of existing expressions, now that someone wants to, I'm going to give you an inverse Polish algorithm.

Our goal is to achieve the following calculation formula:

Suppose you have a formula that reads:

$expression = "(f1*f12+10.34)";

The values of the variables are as follows:

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

We want to build a class with PHP to calculate the value of this expression. This application is primarily used in Web payroll management, where users can customize their payroll-phase formulas.

$RPN = new Math_rpn (); $RPN->setexpressionvalue ($expression _value); echo $rpn->calculate ($expression, ' deg ', false); That is the corresponding value

The method of parsing the inverse Polish expression, the compiler principle is that the expression is decomposed into a symbol array, then the inverse Polish-style, and finally according to the inverse polish to get its results.

I put three functions in the following, in fact, I am the pear rpn function of the hack.

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 () { $time 1 = $this->_getmicrotime (); if ($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]; $time 2 = $this->_getmicrotime (); $this->_timer = $time 2-$time 1; return $this->_value; }

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