perm filename SAILUP.DOC[NET,GUE] blob sn#032735
filedate 1973-03-31 generic text, type T, neo UTF8
C-MU SAIL Manual Update
(Updates C-MU manual dated May, 1970 and Update of 23-AUG-71.)
Feb. 17, 1972
A. The reserved words IFNDEFINE and IFDEFINE have been added.
Syntactically, either may appear any place the word DEFINE can
is identical to the same construct with DEFINE replacing the
IFNDEFINE if the identifier AA has no meaning, i.e., AA has not been
previously declared or defined and it is not a reserved word or
predeclared procedure. If AA already has meaning, the entire
construct has no effect.
The similar construct with IFDEFINE is identical except that
the test is reversed; i.e., the id's are (re)defined only if AA (the
first one) already has meaning, otherwise it is a no-op.
Note that in both cases, the test for the entire construct
depends only on the first id.
(Both this addition and the BIGCOMMENT!--STOPCOMMENT!
constructs were implemented because of a desperate need for some
conditional compilation facilities. They are far from pleasing or
complete; however, they were easy to implement. Within six
months(?), we hope to have a new version of SAIL which has a much
nicer conditional macro facility; in the interim, a surprisingly
large number of things can be done with these primitives. When the
new SAIL arrives, every attempt will be made to retain these
primitives to insure compatability.)