change linebreak

beautiful-racket-demo/basic-demo/expander.rkt

@@ -40,7 +40,8 @@
               (or
                (and (exact-positive-integer? clsv)
                     (vector-member clsv line-vec))
-               (error (format "error in line ~a: line ~a not found"
+               (error
+                (format "error in line ~a: line ~a not found"
                         line-num clsv))))])
         (line-func)
         (add1 line-idx)))))