feat: argument validation

bin/toad.md

@@ -37,10 +37,9 @@ the components of the program are:
 
 print a helpful message if the script is called without an argument
 
-TODO: is `script:get-argument` an array? check to see if length equal zero
-
-    'ARGS s:put nl
-    script:get-argument a:length n:put
+~~~
+script:arguments #0 eq? [ 'Error:_Missing_argument s:put ] if;
+~~~
 
 ## panels