diff options
Diffstat (limited to 'src/ste/Calc.php')
| -rw-r--r-- | src/ste/Calc.php | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/src/ste/Calc.php b/src/ste/Calc.php new file mode 100644 index 0000000..e8dba8d --- /dev/null +++ b/src/ste/Calc.php @@ -0,0 +1,138 @@ +<?php + +namespace kch42\ste; + +/* Class Calc contains static methods needed by <ste:calc /> */ +class Calc { + private function __construct() {} + + /* We could also just eval() the $infix_math code, but this is much cooler :-D (Parser inception) */ + public static function shunting_yard($infix_math) { + $operators = array( + "+" => array("l", 2), + "-" => array("l", 2), + "*" => array("l", 3), + "/" => array("l", 3), + "^" => array("r", 4), + "_" => array("r", 5), + "(" => array("", 0), + ")" => array("", 0) + ); + + preg_match_all("/\s*(?:(?:[+\\-\\*\\/\\^\\(\\)])|(\\d*[\\.]?\\d*))\\s*/s", $infix_math, $tokens, PREG_PATTERN_ORDER); + $tokens_raw = array_filter(array_map('trim', $tokens[0]), function($x) { return ($x === "0") || (!empty($x)); }); + $output_queue = array(); + $op_stack = array(); + + $lastpriority = NULL; + /* Make - unary, if neccessary */ + $tokens = array(); + foreach($tokens_raw as $token) { + $priority = isset($operators[$token]) ? $operators[$token][1] : -1; + if(($token == "-") && (($lastpriority === NULL) || ($lastpriority >= 0))) { + $priority = $operators["_"][1]; + $tokens[] = "_"; + } else { + $tokens[] = $token; + } + $lastpriority = $priority; + } + + while(!empty($tokens)) { + $token = array_shift($tokens); + if(is_numeric($token)) { + $output_queue[] = $token; + } else if($token == "(") { + $op_stack[] = $token; + } else if($token == ")") { + $lbr_found = false; + while(!empty($op_stack)) { + $op = array_pop($op_stack); + if($op == "(") { + $lbr_found = true; + break; + } + $output_queue[] = $op; + } + if(!$lbr_found) { + throw new RuntimeError("Bracket mismatch."); + } + } else if(!isset($operators[$token])) { + throw new RuntimeError("Invalid token ($token): Not a number, bracket or operator. Stop."); + } else { + $priority = $operators[$token][1]; + if($operators[$token][0] == "l") { + while((!empty($op_stack)) and ($priority <= $operators[$op_stack[count($op_stack)-1]][1])) { + $output_queue[] = array_pop($op_stack); + } + } else { + while((!empty($op_stack)) and ($priority < $operators[$op_stack[count($op_stack)-1]][1])) { + $output_queue[] = array_pop($op_stack); + } + } + $op_stack[] = $token; + } + } + + while(!empty($op_stack)) { + $op = array_pop($op_stack); + if($op == "(") { + throw new RuntimeError("Bracket mismatch..."); + } + $output_queue[] = $op; + } + + return $output_queue; + } + + public static function pop2(&$array) { + $rv = array(array_pop($array), array_pop($array)); + if(array_search(NULL, $rv, true) !== false) { + throw new RuntimeError("Not enough numbers on stack. Invalid formula."); + } + return $rv; + } + + public static function calc_rpn($rpn) { + $stack = array(); + foreach($rpn as $token) { + switch($token) { + case "+": + list($b, $a) = self::pop2($stack); + $stack[] = $a + $b; + break; + case "-": + list($b, $a) = self::pop2($stack); + $stack[] = $a - $b; + break; + case "*": + list($b, $a) = self::pop2($stack); + $stack[] = $a * $b; + break; + case "/": + list($b, $a) = self::pop2($stack); + $stack[] = $a / $b; + break; + case "^": + list($b, $a) = self::pop2($stack); + $stack[] = pow($a, $b); + break; + case "_": + $a = array_pop($stack); + if($a === NULL) { + throw new RuntimeError("Not enough numbers on stack. Invalid formula."); + } + $stack[] = -$a; + break; + default: + $stack[] = $token; + break; + } + } + return array_pop($stack); + } + + public static function calc($expr) { + return self::calc_rpn(self::shunting_yard($expr)); + } +}
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