Add defun macro

lib/Minilisp.pm

@@ -331,6 +331,23 @@ sub macro_progn {
 }
 $macros{progn} = \&macro_progn;
 
+sub macro_defun {
+  my $ts = shift;
+
+  my $ident = shift @$ts;
+  die "Expected identifier in defun" unless $ident->{type} == IDENT;
+
+  my $body = macro_lambda($ts);
+
+  return sub {
+    my $ctx = shift;
+    my $fn = $body->($ctx);
+    $ctx->{$ident->{value}} = $fn;
+    return $fn;
+  }
+}
+$macros{defun} = \&macro_defun;
+
 sub compile {
   my ($term) = @_;
   my @tokens = tokenize($term);