diff --git a/bootstrap.php b/bootstrap.php
index 8f0e37d..f292bb4 100644
--- a/bootstrap.php
+++ b/bootstrap.php
@@ -14,9 +14,9 @@ function ml_get_lisp(): array
 
     $env = new MadLisp\Env();
 
-    $core = new MadLisp\Lib\Core();
-    $core->register($env);
+    (new MadLisp\Lib\Math())->register($env);
 
+    /*
     $env->set('eval', function (...$args) use ($eval, $env) {
         $results = $eval->eval($args, $env);
         return $results[count($results) - 1];
@@ -26,6 +26,7 @@ function ml_get_lisp(): array
         $printer->print($args);
         return null;
     });
+    */
 
     return [$lisp, $env];
 }
diff --git a/src/CoreFunc.php b/src/CoreFunc.php
new file mode 100644
index 0000000..9a98538
--- /dev/null
+++ b/src/CoreFunc.php
@@ -0,0 +1,44 @@
+<?php
+namespace MadLisp;
+
+use Closure;
+
+class CoreFunc extends Func
+{
+    protected string $name;
+    protected string $doc;
+    protected int $minArgs;
+    protected int $maxArgs;
+
+    public function __construct(string $name, string $doc, int $minArgs, int $maxArgs, Closure $closure)
+    {
+        $this->name = $name;
+        $this->doc = $doc;
+        $this->minArgs = $minArgs;
+        $this->maxArgs = $maxArgs;
+        $this->closure = $closure;
+    }
+
+    public function call(array $args)
+    {
+        $this->validateArgs(count($args));
+
+        return parent::call($args);
+    }
+
+    private function validateArgs(int $count)
+    {
+        if ($this->minArgs >= 0 && $count < $this->minArgs) {
+            if ($this->minArgs == $this->maxArgs) {
+                throw new MadLispException(sprintf("%s requires exactly %s argument%s", $this->name, $this->minArgs,
+                                                   $this->minArgs == 1 ? '' : 's'));
+            } else {
+                throw new MadLispException(sprintf("%s requires at least %s argument%s", $this->name, $this->minArgs,
+                                                   $this->minArgs == 1 ? '' : 's'));
+            }
+        } elseif ($this->maxArgs >= 0 && $count > $this->maxArgs) {
+                throw new MadLispException(sprintf("%s requires at most %s argument%s", $this->name, $this->maxArgs,
+                                                   $this->maxArgs == 1 ? '' : 's'));
+        }
+    }
+}
diff --git a/src/Evaller.php b/src/Evaller.php
index dc0b119..ce0e5b6 100644
--- a/src/Evaller.php
+++ b/src/Evaller.php
@@ -1,8 +1,6 @@
 <?php
 namespace MadLisp;
 
-use Closure;
-
 class Evaller
 {
     public function eval(array $expressions, Env $env): array
@@ -150,10 +148,10 @@ class Evaller
 
         // Call first argument as function
         $func = $ast->get(0);
-        if (!($func instanceof Closure)) {
+        if (!($func instanceof Func)) {
             throw new MadLispException("first item of list is not function");
         }
         $args = array_slice($ast->getData(), 1);
-        return $func(...$args);
+        return $func->call($args);
     }
 }
diff --git a/src/Func.php b/src/Func.php
new file mode 100644
index 0000000..1f88580
--- /dev/null
+++ b/src/Func.php
@@ -0,0 +1,24 @@
+<?php
+namespace MadLisp;
+
+use Closure;
+
+abstract class Func
+{
+    protected Closure $closure;
+
+    public function __construct(Closure $closure)
+    {
+        $this->closure = $closure;
+    }
+
+    public function getClosure(): Closure
+    {
+        return $this->closure;
+    }
+
+    public function call(array $args)
+    {
+        return ($this->closure)(...$args);
+    }
+}
diff --git a/src/Lib/Core.php b/src/Lib/Core.php
index 0ce5e81..83eb5a3 100644
--- a/src/Lib/Core.php
+++ b/src/Lib/Core.php
@@ -1,8 +1,8 @@
 <?php
 namespace MadLisp\Lib;
 
-use Closure;
 use MadLisp\Env;
+use MadLisp\Func;
 use MadLisp\Hash;
 use MadLisp\MadLispException;
 use MadLisp\MList;
@@ -13,72 +13,8 @@ class Core implements ILib
 {
     public function register(Env $env): void
     {
-        // logic
-
-        $env->set('or', function (...$args) {
-            // return first true
-            for ($i = 0; $i < count($args) - 1; $i++) {
-                if ($args[$i] == true) {
-                    return $args[$i];
-                }
-            }
-
-            // return last
-            return $args[count($args) - 1];
-        });
-
-        $env->set('and', function (...$args) {
-            // return first false
-            for ($i = 0; $i < count($args) - 1; $i++) {
-                if ($args[$i] == false) {
-                    return $args[$i];
-                }
-            }
-
-            // return last
-            return $args[count($args) - 1];
-        });
-
-        $env->set('not', fn ($a) => !$a);
-
         // arithmetic
 
-        $env->set('+', function (...$args) {
-            return array_sum($args);
-        });
-
-        $env->set('-', function (...$args) {
-            $result = $args[0] ?? null;
-            for ($i = 1; $i < count($args); $i++) {
-                $result -= $args[$i];
-            }
-            return $result;
-        });
-
-        $env->set('*', function (...$args) {
-            $result = $args[0] ?? null;
-            for ($i = 1; $i < count($args); $i++) {
-                $result *= $args[$i];
-            }
-            return $result;
-        });
-
-        $env->set('/', function (...$args) {
-            $result = $args[0] ?? null;
-            for ($i = 1; $i < count($args); $i++) {
-                $result /= $args[$i];
-            }
-            return $result;
-        });
-
-        $env->set('%', function (...$args) {
-            $result = $args[0] ?? null;
-            for ($i = 1; $i < count($args); $i++) {
-                $result %= $args[$i];
-            }
-            return $result;
-        });
-
         // comparison
 
         $env->set('=', fn ($a, $b) => $a == $b);
@@ -91,7 +27,7 @@ class Core implements ILib
         // types
 
         $env->set('type?', function ($a) {
-            if ($a instanceof Closure) {
+            if ($a instanceof Func) {
                 return 'function';
             } elseif ($a instanceof MList) {
                 return 'list';
@@ -112,7 +48,7 @@ class Core implements ILib
             }
         });
 
-        $env->set('fn?', fn ($a) => $a instanceof Closure);
+        $env->set('fn?', fn ($a) => $a instanceof Func);
         $env->set('list?', fn ($a) => $a instanceof MList);
         $env->set('hash?', fn ($a) => $a instanceof Hash);
         $env->set('sym?', fn ($a) => $a instanceof Symbol);
@@ -124,14 +60,5 @@ class Core implements ILib
         $env->set('float?', fn ($a) => is_float($a));
         $env->set('str?', fn ($a) => is_string($a));
 
-        // collections
-
-        $env->set('list', function (...$args) {
-            return new MList($args);
-        });
-
-        $env->set('hash', function (...$args) {
-            return Util::makeHash($args);
-        });
     }
 }
diff --git a/src/Lib/Math.php b/src/Lib/Math.php
new file mode 100644
index 0000000..e66dcf5
--- /dev/null
+++ b/src/Lib/Math.php
@@ -0,0 +1,49 @@
+<?php
+namespace MadLisp\Lib;
+
+use MadLisp\CoreFunc;
+use MadLisp\Env;
+
+class Math implements ILib
+{
+    public function register(Env $env): void
+    {
+        // Basic arithmetic
+
+        $env->set('+', new CoreFunc('+', 'Return the sum of all arguments.', 2, -1,
+            function (...$args) {
+                return array_sum($args);
+            }
+        ));
+
+        $env->set('-', new CoreFunc('-', 'Subtract the other arguments from the first.', 2, -1,
+            function (...$args) {
+                return array_reduce(array_slice($args, 1), fn ($a, $b) => $a - $b, $args[0]);
+            }
+        ));
+
+        $env->set('*', new CoreFunc('*', 'Multiply the arguments.', 2, -1,
+            function (...$args) {
+                return array_reduce(array_slice($args, 1), fn ($a, $b) => $a * $b, $args[0]);
+            }
+        ));
+
+        $env->set('/', new CoreFunc('/', 'Divide the arguments.', 2, -1,
+            function (...$args) {
+                return array_reduce(array_slice($args, 1), fn ($a, $b) => $a / $b, $args[0]);
+            }
+        ));
+
+        $env->set('//', new CoreFunc('//', 'Divide the arguments using integer division.', 2, -1,
+            function (...$args) {
+                return array_reduce(array_slice($args, 1), fn ($a, $b) => intdiv($a, $b), $args[0]);
+            }
+        ));
+
+        $env->set('%', new CoreFunc('%', 'Calculate the modulo of arguments.', 2, -1,
+            function (...$args) {
+                return array_reduce(array_slice($args, 1), fn ($a, $b) => $a % $b, $args[0]);
+            }
+        ));
+    }
+}
diff --git a/src/Printer.php b/src/Printer.php
index 30e8883..d6ca9e9 100644
--- a/src/Printer.php
+++ b/src/Printer.php
@@ -1,8 +1,6 @@
 <?php
 namespace MadLisp;
 
-use Closure;
-
 class Printer
 {
     public function print(array $items): void
@@ -14,7 +12,7 @@ class Printer
 
     private function doPrint($a): string
     {
-        if ($a instanceof Closure) {
+        if ($a instanceof Func) {
             return '<function>';
         } elseif ($a instanceof MList) {
             return '(' . implode(' ', array_map(fn ($b) => $this->doPrint($b), $a->getData())) . ')';
diff --git a/src/UserFunc.php b/src/UserFunc.php
new file mode 100644
index 0000000..849e285
--- /dev/null
+++ b/src/UserFunc.php
@@ -0,0 +1,7 @@
+<?php
+namespace MadLisp;
+
+class UserFunc extends Func
+{
+
+}