REBOL 3 Concepts: Functions
There are several kinds of functions provided by REBOL:
|Native||A function that is evaluated directly by the
processor. These are the lowest level functions of the language.
|Function||A higher level function that is defined by a block
and is evaluated by evaluating the functions within the block.
Also called user-defined functions.
|Mezzanine||A name for higher level functions that are a
standard part of the language. These are not native functions.
|Operator||A function that is used as an infix operator.
Examples are +, -, [bad-link:functions/z-gtb-lt.txt] and /.
|Routine||A function that is used to call external library
functions (REBOL/Command feature).