• RenatoL (4/4) Nov 11 2011 int[7] arr = [1,2,3,4,5,6,7];
• Jonathan M Davis (6/11) Nov 11 2011 Probably because it's length is zero and therefore isn't actually a slic...
• RenatoL (3/3) Nov 11 2011 Yes, my fault. As Andrei write on his book
• Steven Schveighoffer (8/21) Nov 11 2011 I would just make a minor correction that it *is* a slice of the origina...
• Nick Sabalausky (4/16) Nov 11 2011 Weird, I was certain that had given me bounds errors before, and so I've...
• Simon (6/24) Nov 11 2011 You get bounds error in debug, but not release.
• Steven Schveighoffer (3/30) Nov 11 2011 There should be no bounds error in any case, an empty slice is valid.
• Steven Schveighoffer (4/5) Nov 11 2011 By "in any case" I meant in either debug or release mode.
• Simon (10/15) Nov 11 2011 even when you index beyond the bounds of the slice?
• Steven Schveighoffer (12/27) Nov 11 2011 You are not reading beyond the valid range. A zero-length slice is
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (7/36) Nov 11 2011 How about Jonathan's this comment: "It wouldn't surprise me if arr[500
• Steven Schveighoffer (4/50) Nov 11 2011 Oh my mistake! I thought we were talking about arr[$..$]!
• Simon (6/56) Nov 12 2011 Yup, that was what I was on about. Should have been a bit clearer on

RenatoL <rexlen gmail.com> writes:

int[7] arr = [1,2,3,4,5,6,7];
writeln(arr[$..$]);

this simply prints a newline... I expected a runtime error (or better
a compile time error) but it does nothing ... why?

Jonathan M Davis <jmdavisProg gmx.com> writes:

On Friday, November 11, 2011 11:46:02 RenatoL wrote:
 int[7] arr = [1,2,3,4,5,6,7];
 writeln(arr[$..$]);
 
 this simply prints a newline... I expected a runtime error (or better
 a compile time error) but it does nothing ... why?

Probably because it's length is zero and therefore isn't actually a slice of 
the original array at all. It wouldn't surprise me if arr[500 .. 500] worked 
exactly the same way. Because the array is empty, it doesn't really matter 
what values you gave it.

- Jonathan M Davis

RenatoL <rexlen gmail.com> writes:

Yes, my fault. As Andrei write on his book

The situation m == n is acceptable and yields an empty slice

Thx.

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Fri, 11 Nov 2011 07:03:33 -0500, Jonathan M Davis <jmdavisProg gmx.com>  
wrote:

 On Friday, November 11, 2011 11:46:02 RenatoL wrote:
 int[7] arr = [1,2,3,4,5,6,7];
 writeln(arr[$..$]);

 this simply prints a newline... I expected a runtime error (or better
 a compile time error) but it does nothing ... why?

 Probably because it's length is zero and therefore isn't actually a  
 slice of
 the original array at all. It wouldn't surprise me if arr[500 .. 500]  
 worked
 exactly the same way. Because the array is empty, it doesn't really  
 matter
 what values you gave it.

I would just make a minor correction that it *is* a slice of the original  
array.  It's just an empty slice.

BTW, I would have expected the output:

[]

(and testing, I see it does do this).

-Steve

"Nick Sabalausky" <a a.a> writes:

"Jonathan M Davis" <jmdavisProg gmx.com> wrote in message 
news:mailman.866.1321013026.24802.digitalmars-d-learn puremagic.com...
 On Friday, November 11, 2011 11:46:02 RenatoL wrote:
 int[7] arr = [1,2,3,4,5,6,7];
 writeln(arr[$..$]);

 this simply prints a newline... I expected a runtime error (or better
 a compile time error) but it does nothing ... why?

 Probably because it's length is zero and therefore isn't actually a slice 
 of
 the original array at all. It wouldn't surprise me if arr[500 .. 500] 
 worked
 exactly the same way. Because the array is empty, it doesn't really matter
 what values you gave it.

Weird, I was certain that had given me bounds errors before, and so I've 
been careful to avoid doing it. Maybe that's changed since I last tried it.

Simon <s.d.hammett gmail.com> writes:

On 11/11/2011 16:56, Nick Sabalausky wrote:
 "Jonathan M Davis"<jmdavisProg gmx.com>  wrote in message
 news:mailman.866.1321013026.24802.digitalmars-d-learn puremagic.com...
 On Friday, November 11, 2011 11:46:02 RenatoL wrote:
 int[7] arr = [1,2,3,4,5,6,7];
 writeln(arr[$..$]);

 this simply prints a newline... I expected a runtime error (or better
 a compile time error) but it does nothing ... why?

 Probably because it's length is zero and therefore isn't actually a slice
 of
 the original array at all. It wouldn't surprise me if arr[500 .. 500]
 worked
 exactly the same way. Because the array is empty, it doesn't really matter
 what values you gave it.

 Weird, I was certain that had given me bounds errors before, and so I've
 been careful to avoid doing it. Maybe that's changed since I last tried it.

You get bounds error in debug, but not release.
The bit about slices says you must not depend on bounds checking.

-- 
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Fri, 11 Nov 2011 13:29:17 -0500, Simon <s.d.hammett gmail.com> wrote:

 On 11/11/2011 16:56, Nick Sabalausky wrote:
 "Jonathan M Davis"<jmdavisProg gmx.com>  wrote in message
 news:mailman.866.1321013026.24802.digitalmars-d-learn puremagic.com...
 On Friday, November 11, 2011 11:46:02 RenatoL wrote:
 int[7] arr = [1,2,3,4,5,6,7];
 writeln(arr[$..$]);

 this simply prints a newline... I expected a runtime error (or better
 a compile time error) but it does nothing ... why?

 Probably because it's length is zero and therefore isn't actually a  
 slice
 of
 the original array at all. It wouldn't surprise me if arr[500 .. 500]
 worked
 exactly the same way. Because the array is empty, it doesn't really  
 matter
 what values you gave it.

 Weird, I was certain that had given me bounds errors before, and so I've
 been careful to avoid doing it. Maybe that's changed since I last tried  
 it.

 You get bounds error in debug, but not release.
 The bit about slices says you must not depend on bounds checking.

There should be no bounds error in any case, an empty slice is valid.

-Steve

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Fri, 11 Nov 2011 14:01:42 -0500, Steven Schveighoffer  
<schveiguy yahoo.com> wrote:

 There should be no bounds error in any case, an empty slice is valid.

By "in any case" I meant in either debug or release mode.

-Steve

Simon <s.d.hammett gmail.com> writes:

On 11/11/2011 19:04, Steven Schveighoffer wrote:
 On Fri, 11 Nov 2011 14:01:42 -0500, Steven Schveighoffer
 <schveiguy yahoo.com> wrote:

 There should be no bounds error in any case, an empty slice is valid.

 By "in any case" I meant in either debug or release mode.

 -Steve

even when you index beyond the bounds of the slice?

you may not actually be reading memory because it's zero length, but 
it's still logically invalid; you've gone outside the valid range.

in vc9, if you increment an iterator beyond the valid range you get a 
debug assert. that's caught quite a few bugs where I work when we 
upgraded to vc9.

-- 
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Fri, 11 Nov 2011 16:10:12 -0500, Simon <s.d.hammett gmail.com> wrote:

 On 11/11/2011 19:04, Steven Schveighoffer wrote:
 On Fri, 11 Nov 2011 14:01:42 -0500, Steven Schveighoffer
 <schveiguy yahoo.com> wrote:

 There should be no bounds error in any case, an empty slice is valid.

 By "in any case" I meant in either debug or release mode.

 -Steve

 even when you index beyond the bounds of the slice?

 you may not actually be reading memory because it's zero length, but  
 it's still logically invalid; you've gone outside the valid range.

You are not reading beyond the valid range.  A zero-length slice is  
perfectly legal to point at the end of an array or other slice.  Reading  
any data from a zero-length slice will cause an out-of-bounds error in  
debug mode, because it has no elements.

 in vc9, if you increment an iterator beyond the valid range you get a  
 debug assert. that's caught quite a few bugs where I work when we  
 upgraded to vc9.

I think you are misunderstanding what the $ actually means.

It's the equivalent in C++ iterators to x.end.

The pair of iterators x.end, x.end is a valid range.  Going *beyond* x.end  
would be illegal.  But iterating *to* x.end is legal (which would be the  
equivalent of [$..$] range), and you will not be able to convince me that  
vc9 doesn't allow it.

-Steve

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 11/11/2011 01:42 PM, Steven Schveighoffer wrote:
 On Fri, 11 Nov 2011 16:10:12 -0500, Simon <s.d.hammett gmail.com> wrote:

 On 11/11/2011 19:04, Steven Schveighoffer wrote:
 On Fri, 11 Nov 2011 14:01:42 -0500, Steven Schveighoffer
 <schveiguy yahoo.com> wrote:

 There should be no bounds error in any case, an empty slice is valid.

 By "in any case" I meant in either debug or release mode.

 -Steve

 even when you index beyond the bounds of the slice?

 you may not actually be reading memory because it's zero length, but
 it's still logically invalid; you've gone outside the valid range.

 You are not reading beyond the valid range. A zero-length slice is
 perfectly legal to point at the end of an array or other slice. Reading
 any data from a zero-length slice will cause an out-of-bounds error in
 debug mode, because it has no elements.

 in vc9, if you increment an iterator beyond the valid range you get a
 debug assert. that's caught quite a few bugs where I work when we
 upgraded to vc9.

 I think you are misunderstanding what the $ actually means.

 It's the equivalent in C++ iterators to x.end.

 The pair of iterators x.end, x.end is a valid range. Going *beyond*
 x.end would be illegal. But iterating *to* x.end is legal (which would
 be the equivalent of [$..$] range), and you will not be able to convince
 me that vc9 doesn't allow it.

 -Steve

How about Jonathan's this comment: "It wouldn't surprise me if arr[500 
.. 500] worked exactly the same way. Because the array is empty, it 
doesn't really matter  what values you gave it."

I think Simon is objecting to 500..500 being accepted (if at all). I 
agree that $..$ is correct.

Ali

Steven Schveighoffer <schveiguy yahoo.com > writes:

Ali Çehreli Wrote:

 On 11/11/2011 01:42 PM, Steven Schveighoffer wrote:
 On Fri, 11 Nov 2011 16:10:12 -0500, Simon <s.d.hammett gmail.com> wrote:

 On 11/11/2011 19:04, Steven Schveighoffer wrote:
 On Fri, 11 Nov 2011 14:01:42 -0500, Steven Schveighoffer
 <schveiguy yahoo.com> wrote:

 There should be no bounds error in any case, an empty slice is valid.

 By "in any case" I meant in either debug or release mode.

 -Steve

 even when you index beyond the bounds of the slice?

 you may not actually be reading memory because it's zero length, but
 it's still logically invalid; you've gone outside the valid range.

 You are not reading beyond the valid range. A zero-length slice is
 perfectly legal to point at the end of an array or other slice. Reading
 any data from a zero-length slice will cause an out-of-bounds error in
 debug mode, because it has no elements.

 in vc9, if you increment an iterator beyond the valid range you get a
 debug assert. that's caught quite a few bugs where I work when we
 upgraded to vc9.

 I think you are misunderstanding what the $ actually means.

 It's the equivalent in C++ iterators to x.end.

 The pair of iterators x.end, x.end is a valid range. Going *beyond*
 x.end would be illegal. But iterating *to* x.end is legal (which would
 be the equivalent of [$..$] range), and you will not be able to convince
 me that vc9 doesn't allow it.

 -Steve

 
 How about Jonathan's this comment: "It wouldn't surprise me if arr[500 
 .. 500] worked exactly the same way. Because the array is empty, it 
 doesn't really matter  what values you gave it."
 
 I think Simon is objecting to 500..500 being accepted (if at all). I 
 agree that $..$ is correct.
 
 Ali

Oh my mistake!  I thought we were talking about arr[$..$]!

Yes, arr[500..500] would result in bounds errors if the array is only 7
elements. When I read it I thought it was just an arbitrary example to show
another way to get an empty slice with an assumption that 500 is a valid index. 

-Steve

Simon <s.d.hammett gmail.com> writes:

On 11/11/2011 23:23, Steven Schveighoffer wrote:
 Ali Çehreli Wrote:

 On 11/11/2011 01:42 PM, Steven Schveighoffer wrote:
 On Fri, 11 Nov 2011 16:10:12 -0500, Simon<s.d.hammett gmail.com>  wrote:

 On 11/11/2011 19:04, Steven Schveighoffer wrote:
 On Fri, 11 Nov 2011 14:01:42 -0500, Steven Schveighoffer
 <schveiguy yahoo.com>  wrote:

 There should be no bounds error in any case, an empty slice is valid.

 By "in any case" I meant in either debug or release mode.

 -Steve

 even when you index beyond the bounds of the slice?

 you may not actually be reading memory because it's zero length, but
 it's still logically invalid; you've gone outside the valid range.

 You are not reading beyond the valid range. A zero-length slice is
 perfectly legal to point at the end of an array or other slice. Reading
 any data from a zero-length slice will cause an out-of-bounds error in
 debug mode, because it has no elements.

 in vc9, if you increment an iterator beyond the valid range you get a
 debug assert. that's caught quite a few bugs where I work when we
 upgraded to vc9.

 I think you are misunderstanding what the $ actually means.

 It's the equivalent in C++ iterators to x.end.

 The pair of iterators x.end, x.end is a valid range. Going *beyond*
 x.end would be illegal. But iterating *to* x.end is legal (which would
 be the equivalent of [$..$] range), and you will not be able to convince
 me that vc9 doesn't allow it.

 -Steve

 How about Jonathan's this comment: "It wouldn't surprise me if arr[500
 .. 500] worked exactly the same way. Because the array is empty, it
 doesn't really matter  what values you gave it."

 I think Simon is objecting to 500..500 being accepted (if at all). I
 agree that $..$ is correct.

 Ali

 Oh my mistake!  I thought we were talking about arr[$..$]!

 Yes, arr[500..500] would result in bounds errors if the array is only 7
elements. When I read it I thought it was just an arbitrary example to show
another way to get an empty slice with an assumption that 500 is a valid index.

 -Steve

Yup, that was what I was on about. Should have been a bit clearer on 
that. Ta.

-- 
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk