Re: error when std.range.Cycle of static array is a member

[Lutger Blijdestijn]

Steven Schveighoffer wrote:

 On Mon, 25 Jul 2011 11:25:17 -0400, Steven Schveighoffer
 schvei...@yahoo.com wrote:
 
 
 Please file a 'rejects-valid' bug.
 
 http://d.puremagic.com/issues/show_bug.cgi?id=6385

Thanks, I'm sorry for slacking, have been a bit busy the last couple of 
days.

Re: error when std.range.Cycle of static array is a member

[Steven Schveighoffer]

On Mon, 25 Jul 2011 11:25:17 -0400, Steven Schveighoffer  
schvei...@yahoo.com wrote:




Please file a 'rejects-valid' bug.


http://d.puremagic.com/issues/show_bug.cgi?id=6385

Re: error when std.range.Cycle of static array is a member

[Steven Schveighoffer]

On Sun, 24 Jul 2011 10:51:32 -0400, Lutger Blijdestijn  
lutger.blijdest...@gmail.com wrote:



Jonathan M Davis wrote:


On Sunday 24 July 2011 12:06:47 Lutger Blijdestijn wrote:

I'm trying to have a Cycle range of a static array as a struct member,
but getting a compilation error. Can anybody tell me if I'm doing
something wrong, or is this a bug?

import std.range;

struct Foo
{
ubyte[] buf;
Cycle!(typeof(buf)) cbuf1; // ok

ubyte[1024] staticBuf;
Cycle!(typeof(staticBuf)) cbuf2; // error

void test()
{
Cycle!(typeof(staticBuf)) cbuf3;
cbuf3 = cycle(staticBuf); // ok
}
}

/std/range.d(228): Error: template instance
std.array.front!(ubyte[1024u]) incompatible arguments for template
instantiation


static arrays are not ranges. You can't pop the front off of them, so no
range- based algorithm would work with a static range. Now, you _can_  
get

a dynamic range over a static range and _that_ is a valid range, so what
you need to do is make the Cycle a Cycle!(ubyte[]) rather than
Cycle!(ubyte[1024]), and you when you pass the static array to cycle,  
you

need to slice it: cycle(staticBuf[]).

- Jonathan M Davis


That would work, but the docs explicitly mention that Cycle is  
specialized

for static arrays (for performance reasons). This is how cycle is
implemented:

Cycle!(R) cycle(R)(ref R input, size_t index = 0) if (isStaticArray!R)
{
return Cycle!(R)(input, index);
}


This is definitely a bug.  In fact, it's a regression, since it passes on  
2.051 (fails on 2.052 and later).  The error is occurring during the  
execution of the *template constraint*.


Reduced case:

import std.range;

pragma(msg, isInputRange!(ubyte[2u]).stringof);

If it's not a bug in dmd (or rather it's the result of a fixed bug), then  
it's a bug in Phobos' isInputRange implementation.  However, I doubt  
that.  Also, the same line works in the context of a function:


import std.range;

void main()
{
   pragma(msg, isInputRange!(ubyte[2u]).stringof); // no error
}

Please file a 'rejects-valid' bug.

-Steve

error when std.range.Cycle of static array is a member

[Lutger Blijdestijn]

I'm trying to have a Cycle range of a static array as a struct member, but 
getting a compilation error. Can anybody tell me if I'm doing something 
wrong, or is this a bug?

import std.range;

struct Foo
{
ubyte[] buf;
Cycle!(typeof(buf)) cbuf1; // ok

ubyte[1024] staticBuf;
Cycle!(typeof(staticBuf)) cbuf2; // error

void test()
{
Cycle!(typeof(staticBuf)) cbuf3;
cbuf3 = cycle(staticBuf); // ok
}
}

/std/range.d(228): Error: template instance std.array.front!(ubyte[1024u]) 
incompatible arguments for template instantiation

Re: error when std.range.Cycle of static array is a member

[Lutger Blijdestijn]

Jonathan M Davis wrote:

 On Sunday 24 July 2011 12:06:47 Lutger Blijdestijn wrote:
 I'm trying to have a Cycle range of a static array as a struct member,
 but getting a compilation error. Can anybody tell me if I'm doing
 something wrong, or is this a bug?
 
 import std.range;
 
 struct Foo
 {
 ubyte[] buf;
 Cycle!(typeof(buf)) cbuf1; // ok
 
 ubyte[1024] staticBuf;
 Cycle!(typeof(staticBuf)) cbuf2; // error
 
 void test()
 {
 Cycle!(typeof(staticBuf)) cbuf3;
 cbuf3 = cycle(staticBuf); // ok
 }
 }
 
 /std/range.d(228): Error: template instance
 std.array.front!(ubyte[1024u]) incompatible arguments for template
 instantiation
 
 static arrays are not ranges. You can't pop the front off of them, so no
 range- based algorithm would work with a static range. Now, you _can_ get
 a dynamic range over a static range and _that_ is a valid range, so what
 you need to do is make the Cycle a Cycle!(ubyte[]) rather than
 Cycle!(ubyte[1024]), and you when you pass the static array to cycle, you
 need to slice it: cycle(staticBuf[]).
 
 - Jonathan M Davis

That would work, but the docs explicitly mention that Cycle is specialized 
for static arrays (for performance reasons). This is how cycle is 
implemented:

Cycle!(R) cycle(R)(ref R input, size_t index = 0) if (isStaticArray!R)
{
return Cycle!(R)(input, index);
}