Oops. I got bitten so I'd better warn:
When you include a file like this:
println$ "Before";
include "./myfile1";
include "./myfile2";
println "After";
The output is:
myfile2
myfile1
Before
After
That's not what I expected being too used to C #include. There's a reason
of course.
Felix automatically includes a file only once. This is so you can
include a file safely if you need it, even if some other file you include
also includes it.
In that scenario, you cannot do stuff like this:
class X { include "a"; }
class Y { include "a"; }
Given the option of including things from multiple places
with automatic removal of duplications, its clear that you also
cannot depend on the order of inclusion either. In fact
inclusions can be mutually recursive. No problem!
This is necessary in a library if you write two modules
that depend on each other: each must include the other.
For function definitions, this is just fine because of setwise lookup.
So the order doesn't matter.
So what Felix *actually* does is pack included files BEFORE
the including file. So what you can rely on is that if you include
a file any variables initialised in it will be initialised FIRST,
before anything in the including file IF and ONLY IF the
including file is not in a cycle with the included file.
The rule is quite specific. Given a set of library files
you can include them and depend on any variables in them
being initialised. It doesn't matter where you write the include
directive. The order of inclusion matters but you must not
depend on it.
If you're writing mutually dependent files you must NOT
depend on the order of variable initialisation (if you
need variables you must initialise them with functions).
SO this is all logical but it is contrary to my "Good bits" claim that
you can just throw code out into a file. You cant. You can only
throw functions out into a file.
A #include facility could be useful. Unfortunately Dypgen is not
capable of recursion, and it provides no simple way to "stack"
lexbufs. It has been pointed out to me it CAN be done by using
a suitable supplier callback for the lexbuf though.
[The moral of the story is: don't use global variables :]
--
john skaller
skal...@users.sourceforge.net
http://felix-lang.org
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