On 09/11/2011 02:12 PM, Jonathan M Davis wrote:
On Sunday, September 11, 2011 14:00:55 Charles Hixson wrote:
On 09/11/2011 01:25 PM, Vladimir Panteleev wrote:
On Sun, 11 Sep 2011 23:02:37 +0300, Charles Hixson
<[email protected]> wrote:
I can't figure it out from
http://www.digitalmars.com/d/2.0/operatoroverloading.html#Binary
// I assume your data structure looks like this
class Node(Key, Data)
{
Key k;
Node!(Key, Data) left, right;
int level;
// ...
void opBinary!("in")(Key k)
{
if (level == 0) return false;
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From: Charles Hixson<[email protected]>
Newsgroups: digitalmars.D.learn
Subject: Re: defining "in" What is the proper way in D2?
Date: Sun, 11 Sep 2011 14:09:57 -0700
Organization: Digital Mars
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On 09/11/2011 01:33 PM, David Nadlinger wrote:
On 9/11/11 10:25 PM, Vladimir Panteleev wrote:
void opBinary!("in")(Key k)
Shouldn't that be »void opBinary(string op : "in")(Key k)«? Also, you
probably want to use opBinaryRight, because opBinary hooks »if
(container in key)«.
David
And thanks for THIS, too. I'd just started to wonder about the order of
the syntax. After all, the key is in the container, but not conversely.
if (k< key) return k in left;
if (key< k) return k in right;
return true;
}
}
VOID?? I'm going to presume that this should have been bool.
Otherwise, thanks. That was they syntax I couldn't figure out from the
docs.
And, yeah. That's what it looks like. My find code was wrong, because
it should have referenced the node, so what I need to do is move the cod
into the node class. But it was the syntax of defining the opBinary
specialization that was hanging me up. (For some reason I have a hard
time wrapping my mind around template code.)
The "in" operator normally returns a pointer to the value that you're trying
to find (and returns null if it's not there). Making it return bool may work,
but it's going to be a problem for generic code. That's like making
opBinary!"*" return a type different than the types being multiplied. It's just
not how the operator is supposed to be used and could cause problems.
- Jonathan M Davis
OK, but what if the container is supposed to be opaque to external
observers, but you still want to be able to tell whether it contains a
particular item? Doesn't returning a pointer violate encapsulation?
Also, the compiler complained about the declaration, causing me to
currently substitute, thus:
// bool opBinaryRight!("in")(Key k)
bool opBinaryRight(string op)(Key k) if (op == "in")
I swiped that code from std.container.d (which also returns a bool).
As what I'm doing is pretty much like a standard container, this seemed
like a reasonable place to look. I sure hope that this doesn't mean I
need to instantiate every use of in. If that's the case I might be
better off just staying with find.
