Re: appending newly initialized struct to array
On Wednesday, 18 April 2012 at 04:55:23 UTC, Ali Çehreli wrote:
On 04/17/2012 02:00 PM, simendsjo wrote:
Sounds like a bug. C style initializers work in other cases:
I try not to use them. I think they have this 'feature' of
leaving unspecified members uninitialized:
struct S
{
int i;
double d;
}
void main()
{
S s = { 42 }; // -- no initializer for S.d
assert(s.i == 42);
assert(s.d == double.nan); // -- fails (may work for you)
You should use std.math.isNaN whether a floating point value is
NaN.
assert(isNaN(s.d)); // -- success
}
Is that a bug or a feature? I might have opened it but I don't
remember now. :)
Ali
Bye.
Kenji Hara
Re: appending newly initialized struct to array
Le 18/04/2012 12:41, maarten van damme a écrit :
That's a very odd design. Making it work when instantiating a new struct
of that type but not inline. Anyway, test(3,5) works perfect, thank you.
It's not odd at all. You append a structure, not an array.
{3,5} is for array initialization, it's the same syntax as in C, C++,
Java, C#.
What if you want to append an array of structures ?
why~=[test(3,5), test(3,6)];
Re: appending newly initialized struct to array
On 04/18/2012 12:16 AM, Kenji Hara wrote: On Wednesday, 18 April 2012 at 04:55:23 UTC, Ali Çehreli wrote: assert(s.d == double.nan); // -- fails (may work for you) You should use std.math.isNaN whether a floating point value is NaN. assert(isNaN(s.d)); // -- success That a thousandth time I have made that mistake and still have not learned. :( Yes, .nan may not be compared with any other value, including .nan. Ali
Re: appending newly initialized struct to array
Ali: That a thousandth time I have made that mistake and still have not learned. :( Yes, .nan may not be compared with any other value, including .nan. Today I'll present an enhancement request to remove this problem from D. Hugs, bearophile
Re: appending newly initialized struct to array
On Wednesday, 18 April 2012 at 16:36:39 UTC, bearophile wrote: Ali: That a thousandth time I have made that mistake and still have not learned. :( Yes, .nan may not be compared with any other value, including .nan. Today I'll present an enhancement request to remove this problem from D. Hugs, bearophile I don't see how this could be enhanced.
Re: appending newly initialized struct to array
On Wednesday, April 18, 2012 19:04:12 SomeDude wrote: On Wednesday, 18 April 2012 at 16:36:39 UTC, bearophile wrote: Ali: That a thousandth time I have made that mistake and still have not learned. :( Yes, .nan may not be compared with any other value, including .nan. Today I'll present an enhancement request to remove this problem from D. Hugs, bearophile I don't see how this could be enhanced. It's by design. An enhancement request is a waste of time. Comparisons with NaN _always_ return false regardless of what they're compared against - even NaN. It's not going to change. - Jonathan M Davis
Re: appending newly initialized struct to array
On Wednesday, 18 April 2012 at 18:18:44 UTC, Ali Çehreli wrote: On 04/18/2012 10:13 AM, Jonathan M Davis wrote: It's by design. An enhancement request is a waste of time. Comparisons with NaN _always_ return false regardless of what they're compared against - even NaN. It's not going to change. - Jonathan M Davis It shouldn't be a problem to detect comparisons against literal .nan values. The compiler can warn with comparison is always false. Ali Now THAT makes sense.
Re: appending newly initialized struct to array
On Wed, Apr 18, 2012 at 08:50:10PM +0200, SomeDude wrote: On Wednesday, 18 April 2012 at 18:18:44 UTC, Ali Çehreli wrote: On 04/18/2012 10:13 AM, Jonathan M Davis wrote: It's by design. An enhancement request is a waste of time. Comparisons with NaN _always_ return false regardless of what they're compared against - even NaN. It's not going to change. - Jonathan M Davis It shouldn't be a problem to detect comparisons against literal .nan values. The compiler can warn with comparison is always false. Ali Now THAT makes sense. +1. T -- Computer Science is no more about computers than astronomy is about telescopes. -- E.W. Dijkstra
Re: appending newly initialized struct to array
SomeDude: It shouldn't be a problem to detect comparisons against literal .nan values. The compiler can warn with comparison is always false. Ali Now THAT makes sense. That's what my proposal is going to be, with small refinements :-) (And it think it's not the first time someone proposes it). Bye, bearophile
Re: appending newly initialized struct to array
On Wednesday, April 18, 2012 11:18:44 Ali Çehreli wrote: On 04/18/2012 10:13 AM, Jonathan M Davis wrote: On Wednesday, April 18, 2012 19:04:12 SomeDude wrote: On Wednesday, 18 April 2012 at 16:36:39 UTC, bearophile wrote: Ali: That a thousandth time I have made that mistake and still have not learned. :( Yes, .nan may not be compared with any other value, including .nan. Today I'll present an enhancement request to remove this problem from D. Hugs, bearophile I don't see how this could be enhanced. It's by design. An enhancement request is a waste of time. Comparisons with NaN _always_ return false regardless of what they're compared against - even NaN. It's not going to change. - Jonathan M Davis It shouldn't be a problem to detect comparisons against literal .nan values. The compiler can warn with comparison is always false. Yes, that would make sense. Heck, I'd be tempted to argue that using == with floating point values in general should be a warning, since that's pretty much never what you actually want, but that's probably not going to fly. But the behavior itself isn't going to change. - Jonathan M Davis
Re: appending newly initialized struct to array
On Tue, Apr 17, 2012 at 10:28:31PM +0200, maarten van damme wrote:
Just for fun I decided to complete some codejam challenges in D. At
some point I wanted to add structs to an array but I got a compiler
error. What am I doing wrong?
code:
struct test{
int x;
int y;
}
void main(){
test[] why;
why~={3,5};
}
error:
wait.d(7): found '}' when expecting ';' following statement
wait.d(8): found 'EOF' when expecting ';' following statement
wait.d(8): found 'EOF' when expecting '}' following compound statement
Is there any reason a why this wouldn't work?
Try this:
why ~= test(3,5);
T
--
Tell me and I forget. Teach me and I remember. Involve me and I understand. --
Benjamin Franklin
Re: appending newly initialized struct to array
On Tue, 17 Apr 2012 22:28:31 +0200, maarten van damme
maartenvd1...@gmail.com wrote:
Just for fun I decided to complete some codejam challenges in D. At some
point I wanted to add structs to an array but I got a compiler error.
What
am I doing wrong?
code:
struct test{
int x;
int y;
}
void main(){
test[] why;
why~={3,5};
}
error:
wait.d(7): found '}' when expecting ';' following statement
wait.d(8): found 'EOF' when expecting ';' following statement
wait.d(8): found 'EOF' when expecting '}' following compound statement
Is there any reason a why this wouldn't work?
Sounds like a bug. C style initializers work in other cases:
struct S { int i; }
void main() {
S[] arr;
S s = { 1 };
arr ~= S(1);
// But the following barfs
//arr ~= { 1 };
//arr ~= { i:1 };
//arr[0] = { 1 };
}
Re: appending newly initialized struct to array
simendsjo: Sounds like a bug. C style initializers work in other cases: D language is so much irregular, so many special cases that don't work :-) Bye, bearophile
Re: appending newly initialized struct to array
On Tuesday, 17 April 2012 at 21:00:55 UTC, simendsjo wrote:
On Tue, 17 Apr 2012 22:28:31 +0200, maarten van damme
maartenvd1...@gmail.com wrote:
Just for fun I decided to complete some codejam challenges in
D. At some
point I wanted to add structs to an array but I got a compiler
error. What
am I doing wrong?
code:
struct test{
int x;
int y;
}
void main(){
test[] why;
why~={3,5};
}
error:
wait.d(7): found '}' when expecting ';' following statement
wait.d(8): found 'EOF' when expecting ';' following statement
wait.d(8): found 'EOF' when expecting '}' following compound
statement
Is there any reason a why this wouldn't work?
Sounds like a bug. C style initializers work in other cases:
struct S { int i; }
void main() {
S[] arr;
S s = { 1 };
arr ~= S(1);
// But the following barfs
//arr ~= { 1 };
//arr ~= { i:1 };
//arr[0] = { 1 };
}
No, it is designed. {3,5} is struct initializer:
http://dlang.org/declaration.html#StructInitializer
And it is only allowed in initializer of variable declarations.
why~={3,5};
This is concat assign expression, so you should use test(3,5)
instead of {3,5}. That is StructLiteral:
http://dlang.org/struct.html#StructLiteral
and it is an expression.
Bye.
Kenji Hara
Re: appending newly initialized struct to array
On 04/17/2012 02:00 PM, simendsjo wrote:
Sounds like a bug. C style initializers work in other cases:
I try not to use them. I think they have this 'feature' of leaving
unspecified members uninitialized:
struct S
{
int i;
double d;
}
void main()
{
S s = { 42 }; // -- no initializer for S.d
assert(s.i == 42);
assert(s.d == double.nan); // -- fails (may work for you)
}
Is that a bug or a feature? I might have opened it but I don't remember
now. :)
Ali
