On Friday, 25 April 2014 at 11:51:48 UTC, bearophile wrote:
They are not the same type:
void main() {
import std.typecons: Tuple;
alias T1 = const Tuple!(int, int);
alias T2 = Tuple!(const int, const int);
static assert(is(T1 == T2)); // Fails.
}
This type difference causes
They are not the same type:
void main() {
import std.typecons: Tuple;
alias T1 = const Tuple!(int, int);
alias T2 = Tuple!(const int, const int);
static assert(is(T1 == T2)); // Fails.
}
This type difference causes some troubles when you use tuples.
Bye,
bearophile
Dicebot:
Why would you even expect those to be same types? These 2 types
are also different:
struct A
{
const int x;
}
alias A_ = const(A);
In general a tuple is a higher level data structure compared to a
struct. So it's not unreasonable to expect a Tuple to be more
flexible than a
On Friday, 25 April 2014 at 12:17:31 UTC, bearophile wrote:
In general a tuple is a higher level data structure compared to
a struct. So it's not unreasonable to expect a Tuple to be more
flexible than a struct.
Well, wrong :) std.typecons.Tuple IS a struct -
Dicebot:
Well, wrong :) std.typecons.Tuple IS a struct -
https://github.com/D-Programming-Language/phobos/blob/master/std/typecons.d#L388
Nope, that's just an implementation detail. They are two quite
different data structures. Example: slicing a tuple always has a
meaning, while slicing a
On Friday, 25 April 2014 at 12:42:33 UTC, bearophile wrote:
Dicebot:
Well, wrong :) std.typecons.Tuple IS a struct -
https://github.com/D-Programming-Language/phobos/blob/master/std/typecons.d#L388
Nope, that's just an implementation detail. They are two quite
different data structures.
Dicebot:
std.typecons.Tuple is just a subset of all structs implementing
specific behavior. It still acts as struct everywhere when
applicable.
A subset is not the same as the whole set.
You are missing something important about what a data structure
is. Take a look at your computer
I was just expressing a little frustration :-)
An example; despite it looks simple I am missing something:
import std.typecons: Tuple, tuple;
import std.algorithm: reduce;
struct Foo { int x; }
auto foo(in Tuple!(Foo[]) arg, int) {
return tuple(arg[0]);
}
void main() {
int[] data;
On Friday, 25 April 2014 at 12:54:25 UTC, bearophile wrote:
Dicebot:
std.typecons.Tuple is just a subset of all structs
implementing specific behavior. It still acts as struct
everywhere when applicable.
A subset is not the same as the whole set.
You are missing something important about
Dicebot:
It would be weird exception of general type system rules with
no practical justification I can readily imagine.
I partially disagree. It could be useful to have structural
typing (http://en.wikipedia.org/wiki/Structural_type_system )
only on tuples (and not on structs), because the
import std.typecons: Tuple, tuple;
import std.algorithm: reduce;
struct Foo { int x; }
auto foo(in Tuple!(Foo[]) arg, int) {
return tuple(arg[0]);
}
void main() {
int[] data;
Foo[] empty;
auto seed = tuple(empty);
reduce!foo(seed, data);
}
I have found a solution:
import
On Friday, 25 April 2014 at 11:51:48 UTC, bearophile wrote:
They are not the same type:
void main() {
import std.typecons: Tuple;
alias T1 = const Tuple!(int, int);
alias T2 = Tuple!(const int, const int);
static assert(is(T1 == T2)); // Fails.
}
This type difference causes
Meta:
I think it's a bad idea to make these equal for this reason: if
T1 == T2, then you would expect Unqual!T1 == Unqual!T2. However:
alias T1 = const Tuple!(int, int);
alias T2 = Tuple!(const int, const int);
assert(is(T1 == T2));
alias UnT1 = Unqual!T1; // Tuple!(int, int)
alias UnT2 =
On Friday, 25 April 2014 at 13:18:13 UTC, bearophile wrote:
Dicebot:
It would be weird exception of general type system rules with
no practical justification I can readily imagine.
I partially disagree. It could be useful to have structural
typing
Dicebot:
For your objections to make sense tuple would need to be
inroduced as completely new first class type system entity. As
this will never happen,
I think first class tuples will happen in D, because the current
tuple situation is quite bad.
But this thread is not about built-in
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