Initial implementation of instruction set

src/Program/Block.php

@@ -24,10 +24,36 @@ class Block
 	}
 
 
-	public function valueOf(string $register): int
+	public function has(string $register): bool
 	{
 		foreach ($this->words as $word) {
 			if ($word->register === $register) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
+
+	public function read(string $register): int
+	{
+		foreach ($this->words as $index => $word) {
+			if ($word->register === $register) {
+				return $word->value;
+			}
+		}
+
+		throw new RuntimeException("No word in block for register '$register'");
+	}
+
+
+	public function pop(string $register): int
+	{
+		foreach ($this->words as $index => $word) {
+			if ($word->register === $register) {
+				unset($this->words[$index]);
+
 				return $word->value;
 			}
 		}
@@ -38,7 +64,7 @@ class Block
 
 	public function __toString()
 	{
-		$buffer = "$this->N\t";
+		$buffer = "N$this->N\t\t";
 		foreach ($this->words as $word) {
 			$buffer .= "$word\t";
 		}