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))
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
If I change it like this:
import std.stdio, std.random, std.array, std.range;
void main() {
string d = "0123456789";
dchar[] res = array(take(randomCover(d, rndGen), 2));
writeln(res);
}
It doesn't work, and gives a cloud of errors:
...\dmd\src\phobos\std\random.d(890): Error:
cast(dchar)(this._input[this._current]) is not an lvalue
...\dmd\src\phobos\std\random.d(907): Error: template std.random.uniform(string
boundaries = "[)",T1,T2,UniformRandomNumberGenerator) if
(is(CommonType!(T1,UniformRandomNumberGenerator) == void) &&
!is(CommonType!(T1,T2) == void)) does not match any function template
declaration
...\dmd\src\phobos\std\random.d(907): Error: template std.random.uniform(string
boundaries = "[)",T1,T2,UniformRandomNumberGenerator) if
(is(CommonType!(T1,UniformRandomNumberGenerator) == void) &&
!is(CommonType!(T1,T2) == void)) cannot deduce template function from argument
types
!()(int,uint,MersenneTwisterEngine!(uint,32,624,397,31,-1727483681u,11,7,-1658038656u,15,-272236544u,18))
If I replace the d string with a dchar[], it works:
import std.stdio, std.random, std.array, std.range;
void main() {
dchar[] d = "0123456789"d.dup;
dchar[] res = array(take(randomCover(d, rndGen), 2));
writeln(res);
}
But now all strings in this little program are dchar arrays.
What I am trying to say is that with the recent changes to the management of
the strings in std.algorithm, when you use strings and char arrays, and you use
algorithms over them, the dchar becomes viral, and you end using in most of the
code composed dchar arrays or dstrings (unless you cast things back to
char[]/string, and I don't know if this is possible in SafeD).
Do you understand now? I am mistaken?
Bye,
bearophile
