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digitalmars.D.learn - opSlice Bug?

reply "Namespace" <rswhite4 googlemail.com> writes:
Why I have to write
arr2[] += arr[][]
instead of
arr2[] += arr[]
? Bug or 'feature'? :P

Code:
http://dpaste.dzfl.pl/4c732f4c
Nov 29 2012
next sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 11/29/2012 08:15 AM, Namespace wrote:

 Why I have to write
 arr2[] += arr[][]
 instead of
 arr2[] += arr[]
 ? Bug or 'feature'? :P

 Code:
 http://dpaste.dzfl.pl/4c732f4c


opSplice, eh? Is that another undocumented feature or one that has been 
deprecated?

Ali
Nov 29 2012
next sibling parent reply "Namespace" <rswhite4 googlemail.com> writes:
On Thursday, 29 November 2012 at 16:46:45 UTC, Ali Çehreli wrote:

 On 11/29/2012 08:15 AM, Namespace wrote:

 Why I have to write
 arr2[] += arr[][]
 instead of
 arr2[] += arr[]
 ? Bug or 'feature'? :P

 Code:
 http://dpaste.dzfl.pl/4c732f4c


 opSplice, eh? Is that another undocumented feature or one that 
 has been deprecated?

 Ali


http://dlang.org/operatoroverloading.html#Slice
Nov 29 2012
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 11/29/2012 08:50 AM, Namespace wrote:

 On Thursday, 29 November 2012 at 16:46:45 UTC, Ali Çehreli wrote:

 On 11/29/2012 08:15 AM, Namespace wrote:

 Why I have to write
 arr2[] += arr[][]
 instead of
 arr2[] += arr[]
 ? Bug or 'feature'? :P

 Code:
 http://dpaste.dzfl.pl/4c732f4c


 opSplice, eh? Is that another undocumented feature or one that has
 been deprecated?

 Ali


 http://dlang.org/operatoroverloading.html#Slice


Thanks. I really did read it as opS_p_lice, found a few references on 
dlang.org, none on any spec page and got a little frustrated. I did not 
realize that I had clearly misread it.

I had even written some notes about opSlice:

   http://ddili.org/ders/d.en/operator_overloading.html

Apparently I had thought that it better returned a special type:

struct Range
{
     // ...
}

struct Container
{
     // For the object[] syntax
     Range opSlice()
     {
         Range allElements;
         // ... must provide access to all elements ...
         return allElements;
     }

/* ... */
}

Ali
Nov 29 2012
parent "Namespace" <rswhite4 googlemail.com> writes:
Yes, that could be better (but I don't like it), but my code 
should compile as well, or not?
Nov 29 2012
prev sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
Ali Çehreli:


 opSplice, eh? Is that another undocumented feature or one that 
 has been deprecated?


I think it's not deprecated:
http://dlang.org/operatoroverloading.html#Slice

Bye,
bearophile
Nov 29 2012
prev sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 11/29/2012 08:15 AM, Namespace wrote:

 Why I have to write
 arr2[] += arr[][]
 instead of
 arr2[] += arr[]
 ? Bug or 'feature'? :P

 Code:
 http://dpaste.dzfl.pl/4c732f4c


Apparently, the array-wise operations require the following syntax:

     a[] += b[];

In other words, the compiler wants to see [] on the right-hand side as 
well. The following does not work with the same error message that you get:

     int[] a, b;
     a[] += b;

Error: invalid array operation a[] += b (did you forget a [] ?)

It is the same in your case. You have a function that returns a slice 
but the compiler still wants to see [] on the rigth-hand side:

int[] foo()
{
     int[] b;
     return b;
}

void main()
{
     int[] a;
     a[] += foo();    // <-- Same compilation error
}

That's why you need to put the [] after it:

     a[] += foo()[];

I think it is just the requirement of the syntax. (?)

Ali
Nov 29 2012
parent "Namespace" <rswhite4 googlemail.com> writes:
That is what I thought also.
That is awfully and limited. :/
Nov 29 2012