diff --git a/lib/Minilisp.pm b/lib/Minilisp.pm
index c724f1a..166a261 100644
--- a/lib/Minilisp.pm
+++ b/lib/Minilisp.pm
@@ -105,6 +105,7 @@ my %stdctx = (
   'null' => sub { my ($a) = @_; return ! defined $a; },
   'evenp' => sub { my ($a) = @_; return ($a % 2 == 0); },
   'oddp' => sub { my ($a) = @_; return ($a % 2 != 0); },
+  'zerop' => sub { my ($a) = @_; return $a == 0; },
   'eq' => sub { my ($a, $b) = @_; return ($a == $b); },
   'ne' => sub { my ($a, $b) = @_; return ($a != $b); },
 
@@ -128,6 +129,24 @@ my %stdctx = (
   '<' => sub { my ($a,$b) = @_; return ($a < $b); },
   '>=' => sub { my ($a,$b) = @_; return ($a >= $b); },
   '<=' => sub { my ($a,$b) = @_; return ($a <= $b); },
+  'max' => sub {
+    die "max: At least 2 parameters" unless scalar(@_) >= 2;
+    my $v = shift;
+    foreach (@_)
+      {
+        $v = $_ if $v < $_;
+      }
+    return $v;
+  },
+  'min' => sub {
+    die "min: At least 2 parameters" unless scalar(@_) >= 2;
+    my $v = shift;
+    foreach (@_)
+      {
+        $v = $_ if $v > $_;
+      }
+    return $v;
+  },
 
   # String comparison
   'string=' => sub { my ($a, $b) = @_; return ($a eq $b); },