From 3c51baa4167d5a68ff010dc81525b9340c5f1329 Mon Sep 17 00:00:00 2001
From: Kevin Chabowski <kevin@kch42.de>
Date: Sat, 24 May 2014 14:45:13 +0200
Subject: Moved code into src subfolder and fixed docu

---
 src/Calc.php | 138 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 src/Calc.php

(limited to 'src/Calc.php')

diff --git a/src/Calc.php b/src/Calc.php
new file mode 100644
index 0000000..e8dba8d
--- /dev/null
+++ b/src/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));
+	}
+}
\ No newline at end of file
-- 
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