attempt to appease vint

exercises/practice/grains/.meta/example.vim

@@ -1,7 +1,7 @@
 " add two strings as numbers from right to left, as if by hand
 function! StringAdd(a, b) abort
   " zero-left-pad so the numbers are the same length
-  let len = [a:a->strlen(), a:b->strlen()]->max()
+  let len = max([strlen(a:a), strlen(a:b)])
   let a = printf('%0*s', len, a:a)
   let b = printf('%0*s', len, a:b)
   let result = ""