How would I sort an associative array by value?

[H. S. Teoh]

On Fri, Sep 06, 2013 at 08:58:48AM +0200, Ludovit Lucenic wrote:
> On Friday, 29 June 2012 at 18:00:06 UTC, Timon Gehr wrote:
> >On 06/29/2012 07:52 PM, ixid wrote:
> >>Or more generally does D have a library function so I can sort one
> >>array based on sorting the contents of another?
> >
> >sort!"a[0]<b[0]"(zip(basedOnThis, alsoSortThis));
> >
> >This sorts both ranges in-place based on the contents of the first
> >range.
> 
> Hello,
> 
> I have a similar problem, having statistics per class instance. How
> would I print out the statistics sorted ?
> 
> struct TestTuple {
>     ...
> }
> 
> int[TestTuple] stats;
> 
> foreach (test, stat; ??) {
>     writeln(test, " = ", stat);
> }
> 
> Please, what comes in ?? ? Your proposal sort!"a[0]<b[0]"(stats)
> does not compile in this place.
[...]

You mean you want to sort the stats.keys by the values they are mapped
to?

What about:

	import std.array, std.algorithm, std.stdio, std.typecons;
	
	// I don't know what your original struct was, this one is just
	// for example.
	struct TestTuple {
		string name;
	}
	
	void main() {
		int[TestTuple] stats;
	
		// Make some sample data for testing
		stats[TestTuple("test1")] = 10;
		stats[TestTuple("test2")] = 4;
		stats[TestTuple("test3")] = 8;
		stats[TestTuple("test4")] = 11;
	
		// Sort by stats. If you want to sort by name instead,
		// change "a[0] < b[0]" to "a[1] < b[1]".
		foreach (t; stats.keys
				.map!((a) => tuple(stats[a], a))
				.array
				.sort!((a,b) => a[0] < b[0]))
		{
			auto stat = t[0];
			auto test = t[1];
			writeln(test, " = ", stat);
		}
	}

The built-in AA's are inherently unordered, so they cannot be sorted
directly. You have to explicitly put the keys / values into an array and
sort that.


T

-- 
Computers shouldn't beep through the keyhole.