digitalmars.D.learn - Variadic function not recognizing static array length

Zach the Mystic (12/12) Mar 12 2013 void func(string[2] a) {}

Zach the Mystic (5/19) Mar 12 2013 I'm just going to assert at runtime instead of at compile time.

=?UTF-8?B?QWxpIMOHZWhyZWxp?= (10/31) Mar 12 2013 Actually, this is not about variadic function templates. The type of an

Zach the Mystic (6/46) Mar 13 2013 Thanks. I see that the type is a slice, but it doesn't stop

Timon Gehr (4/17) Mar 13 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9712

Zach the Mystic (4/27) Mar 14 2013 Man, Hara Kenji is so fast!!!!!! I didn't even know my problem

Zach the Mystic (2/32) Mar 14 2013 (I meant to thank you too, Timon Gehr)

Steven Schveighoffer (8/20) Mar 14 2013 Actually an array literal's default type is a slice, not a fixed-sized

"Zach the Mystic" <reachzach gggggmail.com> writes:

void func(string[2] a) {}

void func2(T...)(T args) {
    static assert(is(typeof(args[0]) == string[2]));
}

void func3(T...)(T args) {
    static assert(args[0].length == 2);
}

func(["",""]); // Okay
func2(["",""]); //  Error: (is(string[] == string[2LU])) is false
func3(["",""]); // Error: _param_0 cannot be read at compile time

Is this the intended design? Is there a workaround which allows 
me to ensure that the parameter is exactly 2 length?

Mar 12 2013

"Zach the Mystic" <reachzach gggggmail.com> writes:

On Tuesday, 12 March 2013 at 21:47:02 UTC, Zach the Mystic wrote:
 void func(string[2] a) {}

 void func2(T...)(T args) {
    static assert(is(typeof(args[0]) == string[2]));
 }

 void func3(T...)(T args) {
    static assert(args[0].length == 2);
 }

 func(["",""]); // Okay
 func2(["",""]); //  Error: (is(string[] == string[2LU])) is 
 false
 func3(["",""]); // Error: _param_0 cannot be read at compile 
 time

 Is this the intended design? Is there a workaround which allows 
 me to ensure that the parameter is exactly 2 length?

I'm just going to assert at runtime instead of at compile time.
assert(args[0].length == 2);

That's a good workaround, only a minor inconvenience it can't be 
caught at compile time.

Mar 12 2013

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

On 03/12/2013 04:10 PM, Zach the Mystic wrote:
 On Tuesday, 12 March 2013 at 21:47:02 UTC, Zach the Mystic wrote:
 void func(string[2] a) {}

 void func2(T...)(T args) {
 static assert(is(typeof(args[0]) == string[2]));
 }

 void func3(T...)(T args) {
 static assert(args[0].length == 2);
 }

 func(["",""]); // Okay
 func2(["",""]); // Error: (is(string[] == string[2LU])) is false
 func3(["",""]); // Error: _param_0 cannot be read at compile time

 Is this the intended design? Is there a workaround which allows me to
 ensure that the parameter is exactly 2 length?

 I'm just going to assert at runtime instead of at compile time.
 assert(args[0].length == 2);

 That's a good workaround, only a minor inconvenience it can't be caught
 at compile time.

Actually, this is not about variadic function templates. The type of an 
array literal is a slice:

     static assert(is(typeof(["",""]) == string[]));

This doesn't help you but it is possible to cast:

     static assert(is(typeof(cast(string[2])["",""]) == string[2]));

or use a variable with an explicit type:

     string[2] var = ["", ""];
     static assert(is(typeof(var) == string[2]));

Ali

Mar 12 2013

"Zach the Mystic" <reachzach gggggmail.com> writes:

On Tuesday, 12 March 2013 at 23:35:28 UTC, Ali Çehreli wrote:
 On 03/12/2013 04:10 PM, Zach the Mystic wrote:
 On Tuesday, 12 March 2013 at 21:47:02 UTC, Zach the Mystic

 wrote:
 void func(string[2] a) {}

 void func2(T...)(T args) {
 static assert(is(typeof(args[0]) == string[2]));
 }

 void func3(T...)(T args) {
 static assert(args[0].length == 2);
 }

 func(["",""]); // Okay
 func2(["",""]); // Error: (is(string[] == string[2LU])) is


 false
 func3(["",""]); // Error: _param_0 cannot be read at compile


 time
 Is this the intended design? Is there a workaround which


 allows me to
 ensure that the parameter is exactly 2 length?

 I'm just going to assert at runtime instead of at compile

 time.
 assert(args[0].length == 2);

 That's a good workaround, only a minor inconvenience it can't

 be caught
 at compile time.

 Actually, this is not about variadic function templates. The 
 type of an array literal is a slice:

     static assert(is(typeof(["",""]) == string[]));

 This doesn't help you but it is possible to cast:

     static assert(is(typeof(cast(string[2])["",""]) == 
 string[2]));

 or use a variable with an explicit type:

     string[2] var = ["", ""];
     static assert(is(typeof(var) == string[2]));

 Ali

Thanks. I see that the type is a slice, but it doesn't stop 
func(string[2]) from taking ["",""] at compile time. I think it 
might have been felt to be problematic not to allow it. I think 
it's inconsistent though. Might be harder to include in complex 
parameter deduction than in explicit parameter lists.

Mar 13 2013

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

On 03/12/2013 10:47 PM, Zach the Mystic wrote:
 void func(string[2] a) {}

 void func2(T...)(T args) {
     static assert(is(typeof(args[0]) == string[2]));
 }

 void func3(T...)(T args) {
     static assert(args[0].length == 2);
 }

 func(["",""]); // Okay
 func2(["",""]); //  Error: (is(string[] == string[2LU])) is false
 func3(["",""]); // Error: _param_0 cannot be read at compile time

 Is this the intended design?

Yes.

 Is there a workaround which allows me to
 ensure that the parameter is exactly 2 length?

http://d.puremagic.com/issues/show_bug.cgi?id=9712
http://d.puremagic.com/issues/show_bug.cgi?id=9711

Mar 13 2013

"Zach the Mystic" <reachzach gggggmail.com> writes:

On Wednesday, 13 March 2013 at 22:14:26 UTC, Timon Gehr wrote:
 On 03/12/2013 10:47 PM, Zach the Mystic wrote:
 void func(string[2] a) {}

 void func2(T...)(T args) {
    static assert(is(typeof(args[0]) == string[2]));
 }

 void func3(T...)(T args) {
    static assert(args[0].length == 2);
 }

 func(["",""]); // Okay
 func2(["",""]); //  Error: (is(string[] == string[2LU])) is 
 false
 func3(["",""]); // Error: _param_0 cannot be read at compile 
 time

 Is this the intended design?

 Yes.

 Is there a workaround which allows me to
 ensure that the parameter is exactly 2 length?

 http://d.puremagic.com/issues/show_bug.cgi?id=9712
 http://d.puremagic.com/issues/show_bug.cgi?id=9711

Man, Hara Kenji is so fast!!!!!! I didn't even know my problem 
wasn't just part of the design, and already it's close to being a 
fixed bug/enhancement!

Mar 14 2013

"Zach the Mystic" <reachzach gggggmail.com> writes:

On Thursday, 14 March 2013 at 20:59:38 UTC, Zach the Mystic wrote:
 On Wednesday, 13 March 2013 at 22:14:26 UTC, Timon Gehr wrote:
 On 03/12/2013 10:47 PM, Zach the Mystic wrote:
 void func(string[2] a) {}

 void func2(T...)(T args) {
   static assert(is(typeof(args[0]) == string[2]));
 }

 void func3(T...)(T args) {
   static assert(args[0].length == 2);
 }

 func(["",""]); // Okay
 func2(["",""]); //  Error: (is(string[] == string[2LU])) is 
 false
 func3(["",""]); // Error: _param_0 cannot be read at compile 
 time

 Is this the intended design?

 Yes.

 Is there a workaround which allows me to
 ensure that the parameter is exactly 2 length?

 http://d.puremagic.com/issues/show_bug.cgi?id=9712
 http://d.puremagic.com/issues/show_bug.cgi?id=9711

 Man, Hara Kenji is so fast!!!!!! I didn't even know my problem 
 wasn't just part of the design, and already it's close to being 
 a fixed bug/enhancement!

(I meant to thank you too, Timon Gehr)

Mar 14 2013

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

On Tue, 12 Mar 2013 17:47:00 -0400, Zach the Mystic  
<reachzach gggggmail.com> wrote:

 void func(string[2] a) {}

 void func2(T...)(T args) {
     static assert(is(typeof(args[0]) == string[2]));
 }

 void func3(T...)(T args) {
     static assert(args[0].length == 2);
 }

 func(["",""]); // Okay
 func2(["",""]); //  Error: (is(string[] == string[2LU])) is false
 func3(["",""]); // Error: _param_0 cannot be read at compile time

 Is this the intended design? Is there a workaround which allows me to  
 ensure that the parameter is exactly 2 length?

Actually an array literal's default type is a slice, not a fixed-sized  
array.  With IFTI, the type is decided by the call, not how you use it the  
parameters.

I filed an enhancement request a while back that would help fix this.

http://d.puremagic.com/issues/show_bug.cgi?id=4998

-Steve

Mar 14 2013

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digitalmars.D.learn - Variadic function not recognizing static array length