Hi, I have now played a around couple of hours (reading everything I
could find) to get something to work, but I think I'm missing some
basic concepts/understanding. Maybe someone can enlighten me how these
things work. I thought that some code from David Nadlinger is what I'm
searching for but don't know how to exactly make use of it.
Here is the code: I want to filter out some of the "allMembers" and use
them in my code for a switch/final to check that call cases that were
not filtered are covered. Trying to build the enum for the switch/final
statement.
auto org_rules = TypeTuple!(__traits(allMembers,BolSource));
static assert(!isTypeTuple!(org_rules));
template startsNotWith(T,char C){
static if (T[0] != C){
enum startsNotWith = true;
} else {
enum startsNotWith = false;
}
}
template StaticFilter(alias pred, T...) {
static if (T.length == 0) {
alias TypeTuple!() StaticFilter;
} else static if (pred!(T[0])) {
alias TypeTuple!(T[0], StaticFilter!(pred, T[1 .. $])) StaticFilter;
} else {
alias StaticFilter!(pred, T[1 .. $]) StaticFilter;
}
}
alias startsNotWithp = startsNotWith!(T,"p"); // doesn't compile:
Error: undefined identifier T
alias rules = StaticFilter!(startsNotWithp, org_rules);
While playing with this a couple of questions came up:
1. How do predicates get their argument(s)? I saw code where only the
predicate was mentioned but no arguments. So, I assume there is some
behind-the-curtain-magic going on. I read about things like "a == b"
where I can reference 'a and 'b in a string.
2. "enum startsNotwith = false" So this is the return syntax for a CTFE
for "return(true)" ?
3. TupleType is a very missleading name when you are learning these
things, because the tuple can hold values as well. Or is there a more
extensive explanation for the name I don't get?
4. Are there any tutorials about CTFE? This seems to be a very powerful
but not so easy to use feature of D, but documentation is quite limited.
Thanks a lot.
--
Robert M. Münch
http://www.saphirion.com
smarter | better | faster
