On 26/04/2012, at 3:21 AM, Raoul Duke wrote:
> seems like the kind of thing you can't get right from the get-go?
Not enough use cases to generalise.
> trying to figure out, as it sounds like you are doing, a flexible
> layout for things so that it can be externalized in libraries and so
> that people can revamp them over time to improve things, that would be
> a nice ground to gain?
There are two, separate, issues: file layout and types.
> how does java do it? does it
> just avoid offering too many useful apis? :-)
Who cares what crud like Java does?
Java barely has a type system compared to Felix.
[Java provides JNI ... enough said ..]
More interesting, what does C++ do?
Ans: it provides ISO Standard interfaces in namespace std,
without stopping you using native C API. It provides UGLY
conditional compilation, and there's provision to use templates
and type traits if you want (though I've not heard of anyone
doing this).
It seems this works:
///////////////////////////////////
// The abstraction, with all the types required
// as parameters, in this case
// os: a phantom type for the os
// u: some os specific type (eg stat_t, fd_t)
class A[os,u] {
virtual fun vf:u -> string;
fun tw(a:u) => "xx " + vf a + " xx";
}
// Now, here's the Windows version
type win = "";
class W {
// windows specific type and functions
type st = "int";
ctor int : st = "$1";
ctor st : int = "$1";
inherit A[win,st]; // grab the abstraction, viewed for Windows
instance A[win,st] { // implement the Windows view
fun vf (x:st) => x.int.str+"w";
}
}
// ditto for Posix
type pos = "";
class P {
type st = "int";
ctor int : st = "$1";
ctor st : int = "$1";
inherit A[pos,st];
instance A[pos,st] {
fun vf (x:st) => x.int.str+"p";
}
}
open W; // Make Windows the default
var x = st 42;
println$ tw x;
var y = P::st 42; // we can still use the Posix version
println$ P::tw y;
/////////////////////////////////////
~/felix>flx a
xx 42w xx
xx 42p xx
/////////////////////////////////
--
john skaller
skal...@users.sourceforge.net
http://felix-lang.org
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