Le 10/02/2023 à 19:50, Brandon Hale a écrit :
Don't be confused by the various implementations of helloword in that
project. Look at the Makefile, only the lisp files are used when
compiling with ecl.
One thing I am confused about with this are all of the #-(and) in
generate.lisp. I know the #+ecl means only run this in ecl, but what do
the #-(and)'s do?
It's a way to comment out a form.
#+ and #- read a boolean feature expression, and then it reads a s-expr
and either ignore it or return it, depending on the value of the boolean
feature expression.
feature expression are either symbols (read in the keyword package or
qualified symbols), that are then tested for membership in the
*features* list; or AND, OR or NOT feature expressions. In the case of
AND and OR, if no subexpressions are present, then they evaluate to the
neutral element, ie, for AND, true, and for OR nil.
So #-(and) means read the following expression only if true is false.
Which is obviously false, so the following expression is ignored.
An equivalent form would be #+(or), which would mean to read the
following expression only of nil is true. Which is false too.
Some people could use #+nil ignored but the problem with #+nil, is that
:NIL could be in *features*, and there was once upon a time a lisp
implementation named New Lisp Implementation and abbreviated as NIL...
--
__Pascal Bourguignon__
