feat: partially implement execution

1 files changed, 42 insertions, 0 deletions

diff --git a/src/Execution/Stack.php b/src/Execution/Stack.php
new file mode 100644
index 0000000..1fa2dae
--- /dev/null
+++ b/src/Execution/Stack.php
@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Nsfisis\Waddiwasi\Execution;
+
+final class Stack
+{
+    /**
+     * @param list<StackEntry> $entries
+     */
+    public function __construct(
+        private array $entries,
+    ) {
+    }
+
+    public function push(StackEntry $entry): void
+    {
+        $this->entries[] = $entry;
+    }
+
+    public function pop(): ?StackEntry
+    {
+        return array_pop($this->entries);
+    }
+
+    public function top(): ?StackEntry
+    {
+        $n = array_key_last($this->entries);
+        return $n === null ? null : $this->entries[$n];
+    }
+
+    public function count(): int
+    {
+        return count($this->entries);
+    }
+
+    public function isEmpty(): bool
+    {
+        return $this->count() === 0;
+    }
+}