From fbc82b017f89f4acb3a43dec746f1742fe8e9a8d Mon Sep 17 00:00:00 2001
From: Lico San <licosan@users.noreply.github.com>
Date: Mon, 17 Jun 2019 10:48:25 +0200
Subject: [PATCH] Create Formula1.php

---
 Formula1.php | 119 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 Formula1.php

diff --git a/Formula1.php b/Formula1.php
new file mode 100644
index 0000000..923dd1b
--- /dev/null
+++ b/Formula1.php
@@ -0,0 +1,119 @@
+<?php
+
+class Formula1 {
+	public $tree=[];
+	private $dual_hp_ops = ['/','*','%','^'];
+	private $dual_lp_ops = ['+','-'];
+	private $single_ops = ['+','-'];
+
+	public function __construct($formula, $params=[], $precision=0, $debug=false) {
+		$this->params = $params;
+		$f = $this->replace_parenth($formula, 0);
+		if(strrpos($f, ')')>-1) {
+			echo('PARSING ERROR: Too many closing parenthesis !');
+			return(false);
+		}
+		$this->tree = $this->parse($f);
+		return(true);
+	}
+
+	private function do_single_op($op, $x){
+		switch($op){
+			case '+': return($x);
+			case '-': return(-$x);
+		}
+	}
+
+	private function do_dual_op($x, $op, $y){
+		switch($op){
+			case '+': return($x+$y);
+			case '-': return($x-$y);
+			case '*': return($x*$y);
+			case '/': return($x/$y);
+			case '%': return($x%$y);
+			case '^': return($x**$y);
+		}
+	}
+
+	private function find_closingp($f, $i0){
+		if(substr($f,$i0,1)!='(') return(false);
+		$level = 0;
+		for($i=$i0+1;$i<strlen($f);$i++) {
+			$c = substr($f,$i,1);
+			if($c== '(') $level++;
+			if($c==')') {
+				if($level==0) return($i);
+				$level--;
+			}
+		}
+		return(false);
+	}
+
+	private function replace_parenth($f, $expr_index){
+		$allops = array_merge($this->dual_lp_ops, $this->dual_hp_ops, $this->single_ops);
+		$nf='';
+		for($i=0;$i<strlen($f);$i++) {
+			$c = substr($f,$i,1);
+			if($c=='(') {
+				$closing_idx = $this->find_closingp($f, $i);
+				if($closing_idx===false) {
+					echo("PARSING ERROR: missing closing parenthesis !");
+					return('');
+				}
+				$expr = substr($f, $i+1, $closing_idx-$i-1);
+				$expr_name = 'expr_'.$expr_index++;
+				$nf.=$expr_name;
+				$this->params[$expr_name] = $this->replace_parenth($expr, $expr_index);
+				$i =  $closing_idx; // let the loop do the +1
+			} else {
+				$nf .= $c;
+			}
+		}
+		return($nf);
+	}
+
+
+	private function parse($f){	
+		$re = '/^(.+?)([\\'.implode('\\',$this->dual_lp_ops).'])(.+)$/'; // dual low priority op
+		if(preg_match($re, $f, $matches, PREG_OFFSET_CAPTURE, 0)){ 
+			return([$this->parse($matches[1][0]), $matches[2][0], $this->parse($matches[3][0])]);
+		} else {
+			$re = '/^(.+?)([\\'.implode('\\',$this->dual_hp_ops).'])(.+)$/'; // dual high priority op
+			if(preg_match($re, $f, $matches, PREG_OFFSET_CAPTURE, 0)){ 
+				return([$this->parse($matches[1][0]), $matches[2][0], $this->parse($matches[3][0])]);
+			} else {
+				$re = '/^([\\'.implode('\\',$this->single_ops).'])(.+)$/'; // single op
+				if(preg_match($re, $f, $matches, PREG_OFFSET_CAPTURE, 0)){ 
+					return([null, $matches[1][0], $this->parse($matches[2][0])]);
+				} else {
+					$re = '/^([A-Za-z][A-Za-z0-9_]*)$/';
+					if(preg_match($re, $f, $matches, PREG_OFFSET_CAPTURE, 0)){ 
+						if(array_key_exists($matches[0][0], $this->params)) return($this->parse($this->params[$matches[0][0]]));
+						else echo('PARSING ERROR: Unknown expression "'.$matches[0][0].'" ');
+					} else {				
+						$re = '/^\d*(\.\d+)?$/'; // unsigned float or int
+						if(preg_match($re, $f, $matches, PREG_OFFSET_CAPTURE, 0)){ 
+							return($matches[0][0]);
+						} else {
+							echo('PARSING ERROR at '.$f.'<br/>');
+						}
+					}
+				}
+			}
+		}
+	}
+
+	private function comp($t) {
+		if(!is_array($t)) return($t);
+		if($t[0]===null) { //unary op
+			return($this->do_single_op($t[1],$this->comp($t[2])));
+		} else {
+			return($this->do_dual_op($this->comp($t[0]), $t[1],$this->comp($t[2])));
+		}
+	}
+
+	public function compute(){
+		return($this->comp($this->tree));
+	}
+
+}