diff --git a/main.c b/main.c
index 4d1f24a..cdd3b2a 100644
--- a/main.c
+++ b/main.c
@@ -745,7 +745,7 @@ static void init_gc(void)
 	alloc_of_type(&empty_list, EMPTY_LIST);
 }
 
-static void display(struct uns_ctr *ctr)
+static void display(struct uns_ctr *ctr, long indent)
 {
 	struct uns_ctr tmp = {0};
 	long l;
@@ -762,13 +762,21 @@ static void display(struct uns_ctr *ctr)
 
 		printf("(");
 		tmp.p = gc.record_get_ptr(ctr->p, 1);
-		display(&tmp);
+		display(&tmp, indent);
 
 		ctr->p = gc.record_get_ptr(ctr->p, 2);
 		while (get_type(ctr->p) == CELL) {
-			printf(" ");
 			tmp.p = gc.record_get_ptr(ctr->p, 1);
-			display(&tmp);
+			if (get_type(tmp.p) == CELL) {
+				printf("\n");
+				for (l = 0; l < indent; l++)
+					printf(" ");
+				display(&tmp, indent + 1);
+			} else {
+				printf(" ");
+				display(&tmp, indent);
+			}
+
 			ctr->p = gc.record_get_ptr(ctr->p, 2);
 		}
 
@@ -778,7 +786,7 @@ static void display(struct uns_ctr *ctr)
 			break;
 		default:
 			printf(" . ");
-			display(ctr);
+			display(ctr, indent);
 			printf(")");
 			break;
 		}
@@ -861,7 +869,7 @@ int main(void)
 		switch (expr_parse(stdin, &expr)) {
 		case EXPR_PARSE_OK:
 			expr.p = gc.record_get_ptr(expr.p, 0);
-			display(&expr);
+			display(&expr, 1);
 			printf("\n");
 			break;
 		case EXPR_PARSE_INCOMPLETE:
diff --git a/prelude.scm b/prelude.scm
index 61aefce..2b413a0 100644
--- a/prelude.scm
+++ b/prelude.scm
@@ -31,7 +31,6 @@
 ; __define-macro: Like __define but for macros
 ; set!
 ; __exec: apply an argument to a lambda and return it to the continuation.
-; __continue-if: continuation version of if.
 ;
 ; Others:
 ; <undefined>: A value that can only be passed to __unilambda. It cannot
@@ -41,12 +40,18 @@
 ;
 ; Macros are functions that return an sexpr.
 
+; (define (__exec function argument continuation)
+;  (continuation (function argument))
+; )
+
+; __continuation-if runs the first continuation if the argument is true,
+; and the second if the argument is false.
 (__define-macro if
  (__unilambda l
-  (__continue-if (car l)
-                 (__unilambda <undefined> (car (cdr l)))
-                 (__unilambda <undefined> (car (cdr (cdr l))))
-  )
+  `(__continue-if ,(car l)
+                 (__unilambda <undefined> ,(car (cdr l)))
+                 (__unilambda <undefined> ,(car (cdr (cdr l))))
+   )
  )
 )