add some time functions

bootstrap.php

@@ -21,6 +21,7 @@ function ml_get_lisp(): array
     (new MadLisp\Lib\Compare())->register($env);
     (new MadLisp\Lib\Math())->register($env);
     (new MadLisp\Lib\Strings())->register($env);
+    (new MadLisp\Lib\Time())->register($env);
     (new MadLisp\Lib\Types())->register($env);
 
     return [$lisp, $env];

src/Lib/Time.php

@@ -0,0 +1,30 @@
+<?php
+namespace MadLisp\Lib;
+
+use MadLisp\CoreFunc;
+use MadLisp\Env;
+
+class Time implements ILib
+{
+    public function register(Env $env): void
+    {
+        $env->set('time', new CoreFunc('time', 'Return the current time as unix timestamp.', 0, 0,
+            fn () => time()
+        ));
+
+        $env->set('date', new CoreFunc('date', 'Format the time according to first argument.', 1, 2,
+            fn (string $format, ?int $time = null) => date($format, $time !== null ? $time : time())
+        ));
+
+        $env->set('strtotime', new CoreFunc('strtotime', 'Parse datetime string into unix timestamp. Optional second argument can be used to give time for relative formats.', 1, 2,
+            fn (string $format, ?int $time = null) => strtotime($format, $time !== null ? $time : time())
+        ));
+
+        $env->set('sleep', new CoreFunc('sleep', 'Sleep (wait) for the specified time in milliseconds.', 1, 1,
+            function (int $time) {
+                usleep($time * 1000);
+                return null;
+            }
+        ));
+    }
+}