Add cond macro

lib/Minilisp.pm

@@ -603,6 +603,43 @@ sub macro_defun {
 }
 $macros{defun} = \&macro_defun;
 
+sub macro_cond {
+  my $ts = shift;
+
+  my @cases;
+  while ($ts->[0]->{type} != RPAREN)
+    {
+      die "Expected ( before case in cond"
+        unless (shift @$ts)->{type} == LPAREN;
+
+      my $condition = parser_expr($ts);
+      my $work = parser_expr($ts);
+
+      die "Expected ) after case in cond"
+        unless (shift @$ts)->{type} == RPAREN;
+
+      push @cases, {
+        condition => $condition,
+        work => $work,
+      };
+    }
+
+  return sub {
+    my $ctx = shift;
+
+    foreach my $case (@cases)
+      {
+        if($case->{condition}->($ctx))
+          {
+            return $case->{work}->($ctx);
+          }
+      }
+
+    return undef;
+  }
+}
+$macros{cond} = \&macro_cond;
+
 sub compile {
   my ($term) = @_;
   my @tokens = tokenize($term);

t/cond.t

@@ -0,0 +1,5 @@
+(expect "cond" 2
+        (cond ((> 1 2) 10)
+              (f 20)
+              ((zerop 0) 2)
+              (t 10)))