In the previous section, we saw that passing the wrong type of argument to a function causes the program to terminate with an error message. Is there a way to guard functions against wrong types and still let the program continue? We know how to test types with type?, so we can do that instead. Here is a version of the inc function that is untyped, but protected against the possibility of n not being an integer:
inc: func [n][ if not integer? n [ print ["n must be an integer, not a" (type? n)] exit ] n + 1]inc 9 ;== 10inc pi ;== n must be an integer, not a floatinc "abc" ;== n must be an integer, not a string
Instead of the if not type? n test, we can also make this somewhat more readable:
inc: func [n][ unless integer ...
