To define a function with argument(s), use the func word, as shown in the following function that performs an increment:
inc: func [n][n + 1] ;== func [n][n + 1]inc ; *** Script Error: inc is missing its n argumentinc 7 ;== 8
Note that a func needs its argument to be passed as a parameter by the calling code; otherwise, you get the error ... is missing its ... argument. But, unlike most other programming languages, you don't have to enclose the parameters in parentheses () when you call the function.
By the way, you'll better understand the : or get word with a function example. The inc word (or better inc n) calls (evaluates) the function, but : returns its own value:
:inc ;== func [n][n + 1]get 'inc ;== func [n][n + 1] ...
