15.10 Conditional Compilation

(if_system SYS-NAME:id TRUE-CASE:any
FALSE-CASE:any): any macro
This is a conditional macro for choosing system dependent code during compilation. The expression for the false case defaults to nil if it is ommited. The id must be a member of the list whose name is system_list*. An example of its use follows.
    (if_system  tops20  (setq buildfileformat⋆ "PL:%W"))