On 09/12/2010 07:09 PM, bearophile wrote:
Andrei Alexandrescu:
This goes into "bearophile's odd posts coming now and then".
I assume you have missed most of the things I was trying to say, maybe you have
not even read the original post. So I try to explain better a subset of the
things I have written.
This is a quite common piece of Python code:
from random import sample
d = "0123456789"
print "".join(sample(d, 2))
Well it's not that common code. How often would one need to generate a
string that contains two random but distinct digits?
I need to perform the same thing in D.
For me it's not easy to do that in D2 with Phobos2.
This doesn't work:
import std.stdio, std.random, std.array, std.range;
void main() {
string d = "0123456789";
string res = array(take(randomCover(d, rndGen), 2));
writeln(res);
}
It returns:
test.d(4): Error: cannot implicitly convert expression
(array(take(randomCover(d,rndGen()),2u))) of type dchar[] to string
The code compiles and runs as written on my system. I think it's David
Simcha who changed the return type to ForEachType!Range[]. I'm not sure
I agree with that, as it takes an oddity of foreach that I hoped would
go away some time and propagates it.
About the original problem: strings are bidirectional ranges of dchar,
which is the way they ought to be. Algorithms used on top of strings
will inherently traffic in dchar. If you want to get a string back, this
should work:
string res = to!string(take(randomCover(d, rndGen), 2));
That doesn't work for a different reason, and is a bug worth filing. In
fact - no need, I just submitted a fix
(http://www.dsource.org/projects/phobos/changeset/1988). Thanks for
bringing this up!
Andrei
