The Design of AIR and its Application to Ada Separate Compilation

AIR, the Ada Intermediate Representat ion in the York Ada Workbench compi le r [ t . 2 . 3 . 4 ] . is the form of an Aria p rogram between the front and back ends of the Ada compi le r , and is also used by other tools which work on Ada programs. AIR was des igned pr imar i ly by Colin Runciman and Chris Johnson in the spr ing of 1981 and rep laced the ear l ie r in termediate representat ion cal led WIT [Walker Intermediate Tree) des igned by lan Walker. The d i f ference between the two was that AIR was des igned to represent p rograms written in revised (1980) Ada [5]; WIT was based on pre l iminary (1979) Aria [6]. Since the init ial des ign, parts of the AIR have been modi f ied to cor respond with the more recent Ada standard [ 7 ] ,