On Tuesday, 21 April 2015 at 17:30:08 UTC, Steven Schveighoffer
wrote:
On 4/21/15 11:25 AM, "Marc =?UTF-8?B?U2Now7x0eiI=?=
<[email protected]>" wrote:
On Tuesday, 21 April 2015 at 14:25:29 UTC, Steven
Schveighoffer wrote:
On 4/21/15 10:07 AM, Chris wrote:
Here's bearophile's version of sorting an AA by value [1]
void main() {
import std.stdio: writeln;
import std.algorithm.sorting: multiSort;
import std.array: array;
const size_t[string] wCount = [
"hamster": 5,
"zorro": 80,
"troll": 90,
"algorithm": 80,
"beer": 80
];
auto pairs = wCount.byKeyValue.array;
assert(wCount.length == pairs.length);
pairs.multiSort!(q{a.value > b.value}, q{a.key < b.key});
assert(pairs[2].key == "beer");
foreach (const ref it; pairs)
writeln(it.key, ": ", it.value);
}
Should we add it to the documentation of
1.
http://dlang.org/phobos/std_algorithm_sorting.html#.multiSort
2. http://dlang.org/hash-map.html
We should not be promoting string-based lambdas:
pairs.multiSort!((a, b) => a.value > b.value, (a, b) => a.key
< b.key);
I find the strings to be more readable, simply because they
are shorter.
I would probably even prefer normal "" quotes.
quoted lambdas are indeed shorter, but the issue with them is
that "a<b" instantiates a different template than "a < b",
whereas the lambda does not.
In fact, that is why we added shorthand lambdas to the
language. Note that in this case, it's just wasted code space
and not a real issue. but for example, RedBlackTree!(int, "a <
b") is not compatible with RedBlackTree!(int, "a<b"), even
though they are identical.
I'm not saying we shouldn't allow string lambdas, just that we
shouldn't encourage them as "proper" D code.
I think this would be a perfect addition for the disqus forum
of that
function (once ddox gets to be the default). I don't want to
get into
adding sample usages for every use case on every function to
the
documentation.
Not for every possible use case, but I'd prefer examples
demonstrating
an actual, practical application to ones that were just made
up for the
sake of documentation.
This use case seems niche to me. I haven't ever had the need to
"sort" an AA, and if I did, I would use a RedBlackTree.
Not discounting it, or saying it's not valid or useful, just
that it's not such a perfect example that it needs to unseat
the current example (sorting points by x and y).
It definitely does not belong in the AA documentation.
-Steve
It's not meant to unseat the existing example, but it could be
added as an additional use case. I agree, I don't need AA.value
sort everyday, but when you need it, it should be fast and easy
to implement. I needed it, because I was grinding data in various
ways (like you would in a spread sheet). It came in handy there.
multiSort should at least be added to the cheat sheet in
std.algorithm.sorting.
