Merge pull request #32 from a1812/interpreter

Add pattern Interpreter/RealWorld

Author: neochief

src/RefactoringGuru/Interpreter/RealWorld/Output.txt

@@ -0,0 +1,2 @@
+boolean expression A ∧ (B ∨ C) = true, with variables A=true, B=true, C=false
+boolean expression B ∨ (A ∧ (B ∨ C)) = false, with variables A=false, B=false, C=true

src/RefactoringGuru/Interpreter/RealWorld/index.php

@@ -0,0 +1,136 @@
+<?php
+
+namespace RefactoringGuru\Interpreter\RealWorld;
+
+/**
+ * EN: Interpreter Design Pattern
+ *
+ * Defines a representation for a grammar as well as a mechanism to understand and act upon the grammar.
+ *
+ * RU: Паттерн Интерпретатор
+ *
+ * Определяет грамматику простого языка, представляет предложения на этом языке и интерпретирует их.
+ */
+class Context
+{
+    private $poolVariable;
+
+    public function lookUp(string $name): bool
+    {
+        if (!key_exists($name, $this->poolVariable)) {
+            die("No exist variable: $name");
+        }
+
+        return $this->poolVariable[$name];
+    }
+
+    public function assign(VariableExp $variable, $val)
+    {
+        $this->poolVariable[$variable->getName()] = $val;
+    }
+}
+
+abstract class AbstractExp
+{
+    abstract public function interpret(Context $context): bool;
+}
+
+class VariableExp extends AbstractExp
+{
+    private $name;
+
+    public function __construct(string $name)
+    {
+        $this->name = $name;
+    }
+
+    public function interpret(Context $context): bool
+    {
+        return $context->lookUp($this->name);
+    }
+
+    public function getName(): string
+    {
+        return $this->name;
+    }
+}
+
+class AndExp extends AbstractExp
+{
+    private $first;
+    private $second;
+
+    public function __construct(AbstractExp $first, AbstractExp $second)
+    {
+        $this->first  = $first;
+        $this->second = $second;
+    }
+
+    public function interpret(Context $context): bool
+    {
+        return (bool)$this->first->interpret($context) && $this->second->interpret($context);
+    }
+}
+
+class OrExp extends AbstractExp
+{
+    private $first;
+    private $second;
+
+    public function __construct(AbstractExp $first, AbstractExp $second)
+    {
+        $this->first  = $first;
+        $this->second = $second;
+    }
+
+    public function interpret(Context $context): bool
+    {
+        return $this->first->interpret($context) || $this->second->interpret($context);
+    }
+}
+
+/**
+ * EN: The client code.
+ *
+ * RU: Клиентский код.
+ */
+
+$context = new Context();
+
+$a = new VariableExp('A');
+$b = new VariableExp('B');
+$c = new VariableExp('C');
+
+// example 1:
+// A ∧ (B ∨ C)
+$exp = new AndExp(
+    $a,
+    new OrExp($b, $c)
+);
+
+$context->assign($a, true);
+$context->assign($b, true);
+$context->assign($c, false);
+
+$result = $exp->interpret($context) ? 'true' : 'false';
+
+echo 'boolean expression A ∧ (B ∨ C) = ' . $result . ', with variables A=true, B=true, C=false' . PHP_EOL;
+
+
+// example 2:
+// B ∨ (A ∧ (B ∨ C))
+$exp = new OrExp(
+    $b,
+    new AndExp(
+        $a,
+        new OrExp($b, $c)
+    )
+);
+
+$context->assign($a, false);
+$context->assign($b, false);
+$context->assign($c, true);
+
+$result2 = $exp->interpret($context) ? 'true' : 'false';
+
+echo 'boolean expression B ∨ (A ∧ (B ∨ C)) = ' . $result2 . ', with variables A=false, B=false, C=true';