• SrMordred (6/6) Feb 21 2018 string x = "123";
• Nicholas Wilson (3/9) Feb 21 2018 youd have to do
• SrMordred (5/9) Feb 21 2018 Nice!
• Steven Schveighoffer (6/19) Feb 21 2018 Hah! I never thought of doing a slice with negative indexes ;)
• joe (8/26) Feb 22 2018 At night I dream about doing something like this
• SrMordred (5/6) Feb 22 2018 Maybe is my past of python:
• Adam D. Ruppe (4/9) Feb 21 2018 But with a slice negative indexes are never allowed, even on a
• Timon Gehr (5/16) Feb 22 2018 Actually, it's slightly more complicated than that. E.g. c[-2..-1] does

SrMordred <patric.dexheimer gmail.com> writes:

string x = "123";
auto c = x.ptr;
c++;
writeln(c[-1]); // 1
writeln(c[-1..0]); //BOOM Range violation


Can I do this / Bug / some mistake ?

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Thursday, 22 February 2018 at 00:13:43 UTC, SrMordred wrote:
 string x = "123";
 auto c = x.ptr;
 c++;
 writeln(c[-1]); // 1
 writeln(c[-1..0]); //BOOM Range violation


 Can I do this / Bug / some mistake ?

youd have to do
(c-1)[0 .. 1];

SrMordred <patric.dexheimer gmail.com> writes:

 But with a slice negative indexes are never allowed, even on a 
 pointer.

 youd have to do
 (c-1)[0 .. 1];

Nice!
Thank you both!

In D Slice article it says "You can even use negative indexes!" 
so I thought
that the [-1..x] should work too :)

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 2/21/18 7:30 PM, SrMordred wrote:
 But with a slice negative indexes are never allowed, even on a pointer.

 
 youd have to do
 (c-1)[0 .. 1];

 
 Nice!
 Thank you both!
 
 In D Slice article it says "You can even use negative indexes!" so I 
 thought
 that the [-1..x] should work too :)
 
 

Hah! I never thought of doing a slice with negative indexes ;)

Note that the statement is about C pointers, so since C doesn't have 
slicing, it stands to reason that slicing with negative indexes isn't 
supported.

-Steve

joe <joe example.com> writes:

On Thursday, 22 February 2018 at 02:41:30 UTC, Steven 
Schveighoffer wrote:
 On 2/21/18 7:30 PM, SrMordred wrote:
 But with a slice negative indexes are never allowed, even on 
 a pointer.

 
 youd have to do
 (c-1)[0 .. 1];

 
 Nice!
 Thank you both!
 
 In D Slice article it says "You can even use negative 
 indexes!" so I thought
 that the [-1..x] should work too :)
 
 

 Hah! I never thought of doing a slice with negative indexes ;)

 /SNIP

 -Steve

At night I dream about doing something like this

auto pos = haystack.find(needle);
auto something = haystack[pos..+3];      // meaning [pos..pos+3]
auto somethingElse = haystack[pos..-3];  // and [pos..pos-3] 
respectively

:)

SrMordred <patric.dexheimer gmail.com> writes:

On Thursday, 22 February 2018 at 02:41:30 UTC, Steven 
Schveighoffer wrote:
 Hah! I never thought of doing a slice with negative indexes ;)

Maybe is my past of python:

arr[-3:] to get the last 3 elements for eg.

:)

Adam D. Ruppe <destructionator gmail.com> writes:

On Thursday, 22 February 2018 at 00:13:43 UTC, SrMordred wrote:
 string x = "123";
 auto c = x.ptr;
 c++;
 writeln(c[-1]); // 1

That's only happening because pointers bypass range checks.

 writeln(c[-1..0]); //BOOM Range violation

But with a slice negative indexes are never allowed, even on a 
pointer.

Timon Gehr <timon.gehr gmx.ch> writes:

On 22.02.2018 01:26, Adam D. Ruppe wrote:
 On Thursday, 22 February 2018 at 00:13:43 UTC, SrMordred wrote:
 string x = "123";
 auto c = x.ptr;
 c++;
 writeln(c[-1]); // 1

 
 That's only happening because pointers bypass range checks.
 
 writeln(c[-1..0]); //BOOM Range violation

 
 But with a slice negative indexes are never allowed, even on a pointer.

Actually, it's slightly more complicated than that. E.g. c[-2..-1] does 
not trigger the range check and will behave as expected. For slices 
c[l..r] there is a check whether cast(size_t)l<=cast(size_t)r. The range 
violation happens because -1 is larger than 0 as an unsigned integer.