<?php class ExpressionCalculator { public function calc($expression) { $operands = array(); while (($token = strtok($expression, ' ')) !== false) { if (isOperator($token)) { $rightOperand = array_pop($operands); $leftOperand = array_pop($operands); $result = $this->execute($token, $leftOperand, $rightOperand); array_push($operands, $result); continue; } array_push($operands, $token); } return $result; } } $calc = new ExpressionCalculator(); echo $calc->calc('5 1 2 + 4 * + 3 -'); // 14
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