• Steve Teale <steve.teale britseyeview.com> Mar 23 2009
• "Unknown W. Brackets" <unknown simplemachines.org> Mar 24 2009
• Steve Teale <steve.teale britseyeview.com> Mar 24 2009
• Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> Mar 24 2009
• "Unknown W. Brackets" <unknown simplemachines.org> Mar 24 2009

Steve Teale <steve.teale britseyeview.com> writes:

bearophile Wrote:

 Steve Teale:
 What am I missing here, isn't char[] a dynamic array?


 I suggest you to post such questions to the "learn" newsgroup.
 
 D dynamic arrays aren't objects, they are C-like structs that contain a just
length and a pointer (no capacity). The "new" for them is needed only to
allocate the memory they point to. So to define an empty dynamic array of chars:
 
 char[] ca;
 In D1 you can also just:
 string s1;
 
 To allocate a non empty array of chars of specified len:
 auto ca = new char[some_len];
 
 Tale a look at the D docs, where such things are explained.
 
 Bye,
 bearophile


So how do you interpret the error message?

"Unknown W. Brackets" <unknown simplemachines.org> writes:

Steve,

It's not exactly prose, but the error message is correct.  It says:

"Error: new can only create structs, dynamic arrays or class objects, 
not char[]'s."

So:

1. You didn't try to allocate space for a struct (e.g. new struct_t.)
2. You didn't try to allocate space for a dynamic array (new char[5].)
3. You didn't try to allocate space for a class object (new Class.)

 From your code, it's obvious what you were meaning to do, so I would 
agree that changing this would be good.  Options I see are:

1. Improve the error message, e.g.: "Error: new can only create structs, 
sized dynamic arrays, or class objects; char[] cannot be created."

2. Change the compiler to react as if you used new char[0].

3. Special case the error message, e.g.: "Error: new can only create 
dynamic arrays with an initial length, use 0 for empty."

-[Unknown]


Steve Teale wrote:
 bearophile Wrote:
 
 Steve Teale:
 What am I missing here, isn't char[] a dynamic array?



 D dynamic arrays aren't objects, they are C-like structs that contain a just
length and a pointer (no capacity). The "new" for them is needed only to
allocate the memory they point to. So to define an empty dynamic array of chars:

 char[] ca;
 In D1 you can also just:
 string s1;

 To allocate a non empty array of chars of specified len:
 auto ca = new char[some_len];

 Tale a look at the D docs, where such things are explained.

 Bye,
 bearophile


 So how do you interpret the error message?
 
 

Steve Teale <steve.teale britseyeview.com> writes:

Unknown W. Brackets Wrote:

 Steve,
 
 It's not exactly prose, but the error message is correct.  It says:
 
 "Error: new can only create structs, dynamic arrays or class objects, 
 not char[]'s."
 
 So:
 
 1. You didn't try to allocate space for a struct (e.g. new struct_t.)
 2. You didn't try to allocate space for a dynamic array (new char[5].)
 3. You didn't try to allocate space for a class object (new Class.)
 
  From your code, it's obvious what you were meaning to do, so I would 
 agree that changing this would be good.  Options I see are:
 
 1. Improve the error message, e.g.: "Error: new can only create structs, 
 sized dynamic arrays, or class objects; char[] cannot be created."
 
 2. Change the compiler to react as if you used new char[0].
 
 3. Special case the error message, e.g.: "Error: new can only create 
 dynamic arrays with an initial length, use 0 for empty."
 


Best answer yet! You win a free holiday in Tanzania (as long as you pay to get
there). Yes it would be great if the error message gave you clue about
specifying the size. Then, all the magic is removed, and you know just where
you are. But even then, zero would be quite a good default!

 -[Unknown]
 
 
 Steve Teale wrote:
 bearophile Wrote:
 
 Steve Teale:
 What am I missing here, isn't char[] a dynamic array?



 D dynamic arrays aren't objects, they are C-like structs that contain a just
length and a pointer (no capacity). The "new" for them is needed only to
allocate the memory they point to. So to define an empty dynamic array of chars:

 char[] ca;
 In D1 you can also just:
 string s1;

 To allocate a non empty array of chars of specified len:
 auto ca = new char[some_len];

 Tale a look at the D docs, where such things are explained.

 Bye,
 bearophile


 So how do you interpret the error message?
 
 

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

Steve Teale wrote:
 Unknown W. Brackets Wrote:
 
 Steve,

 It's not exactly prose, but the error message is correct.  It says:

 "Error: new can only create structs, dynamic arrays or class objects, 
 not char[]'s."

 So:

 1. You didn't try to allocate space for a struct (e.g. new struct_t.)
 2. You didn't try to allocate space for a dynamic array (new char[5].)
 3. You didn't try to allocate space for a class object (new Class.)

  From your code, it's obvious what you were meaning to do, so I would 
 agree that changing this would be good.  Options I see are:

 1. Improve the error message, e.g.: "Error: new can only create structs, 
 sized dynamic arrays, or class objects; char[] cannot be created."

 2. Change the compiler to react as if you used new char[0].

 3. Special case the error message, e.g.: "Error: new can only create 
 dynamic arrays with an initial length, use 0 for empty."


 Best answer yet! You win a free holiday in Tanzania (as long as you pay to get
there). Yes it would be great if the error message gave you clue about
specifying the size. Then, all the magic is removed, and you know just where
you are. But even then, zero would be quite a good default!


I don't mean to ruin anyone's holiday in Tanzania but zero is a crappy 
default. When I say new char[] it's not like I'm really hoping for a 
shortcut for new char[0]. It's more likely new char[] is really 
originating as new T where T = char[].

Andrei

"Unknown W. Brackets" <unknown simplemachines.org> writes:

No, I agree.  I think for the sake of templating, improving the error 
message is the best option - probably #3 (special case error message) imho.

-[Unknown]


Andrei Alexandrescu wrote:
 Steve Teale wrote:
 Unknown W. Brackets Wrote:

 Steve,

 It's not exactly prose, but the error message is correct.  It says:

 "Error: new can only create structs, dynamic arrays or class objects, 
 not char[]'s."

 So:

 1. You didn't try to allocate space for a struct (e.g. new struct_t.)
 2. You didn't try to allocate space for a dynamic array (new char[5].)
 3. You didn't try to allocate space for a class object (new Class.)

  From your code, it's obvious what you were meaning to do, so I would 
 agree that changing this would be good.  Options I see are:

 1. Improve the error message, e.g.: "Error: new can only create 
 structs, sized dynamic arrays, or class objects; char[] cannot be 
 created."

 2. Change the compiler to react as if you used new char[0].

 3. Special case the error message, e.g.: "Error: new can only create 
 dynamic arrays with an initial length, use 0 for empty."


 Best answer yet! You win a free holiday in Tanzania (as long as you 
 pay to get there). Yes it would be great if the error message gave you 
 clue about specifying the size. Then, all the magic is removed, and 
 you know just where you are. But even then, zero would be quite a good 
 default!


 I don't mean to ruin anyone's holiday in Tanzania but zero is a crappy 
 default. When I say new char[] it's not like I'm really hoping for a 
 shortcut for new char[0]. It's more likely new char[] is really 
 originating as new T where T = char[].
 
 Andrei