• Andre Pany (8/8) Dec 22 2020 Hi,
• ag0aep6g (15/20) Dec 22 2020 Looks like an oddity in the grammar.
• Andre Pany (4/20) Dec 22 2020 Thanks a lot!
• Daniel Kozak (6/14) Dec 22 2020 As has been said this is an oddity in the grammar. But why would anyone
• Steven Schveighoffer (4/28) Dec 22 2020 Yeah:
• Daniel Kozak (4/32) Dec 22 2020 Yes AA.init is null per doc.
• Andre Pany (6/18) Dec 23 2020 Thanks for clarification, I was not aware that AA.init is

Andre Pany <andre s-e-a-p.de> writes:

Hi,

I am really confused, why is this valid:
void sample(string[string] s = string[string].init){}

while this causes syntax errors?

void sample_invalid1(double[string] s = double[string].init){}
void sample_invalid2(int[int] s = int[int].init){}

Kind regards
André

ag0aep6g <anonymous example.com> writes:

On Tuesday, 22 December 2020 at 21:11:12 UTC, Andre Pany wrote:
 I am really confused, why is this valid:
 void sample(string[string] s = string[string].init){}

 while this causes syntax errors?

 void sample_invalid1(double[string] s = double[string].init){}
 void sample_invalid2(int[int] s = int[int].init){}

Looks like an oddity in the grammar.

`string` is an alias, meaning it's an identifier. And an 
identifier is a valid expression to the grammar. So 
`string[string]` is parsed as an IndexExpression. Only during 
semantic analysis does the compiler figure out that it's actually 
a type.

`double` and `int` aren't identifiers. They're keywords. And 
they're always types, never expressions. So `int[int]` cannot be 
parsed as an IndexExpression. It's parsed as a Type instead. And 
for a (grammatical) Type, there is no rule that allows 
`Type.Identifier`.

You can work around with parentheses:

(double[string]).init;
(int[int]).init

Andre Pany <andre s-e-a-p.de> writes:

On Tuesday, 22 December 2020 at 22:02:54 UTC, ag0aep6g wrote:
 On Tuesday, 22 December 2020 at 21:11:12 UTC, Andre Pany wrote:
 [...]

 Looks like an oddity in the grammar.

 `string` is an alias, meaning it's an identifier. And an 
 identifier is a valid expression to the grammar. So 
 `string[string]` is parsed as an IndexExpression. Only during 
 semantic analysis does the compiler figure out that it's 
 actually a type.

 `double` and `int` aren't identifiers. They're keywords. And 
 they're always types, never expressions. So `int[int]` cannot 
 be parsed as an IndexExpression. It's parsed as a Type instead. 
 And for a (grammatical) Type, there is no rule that allows 
 `Type.Identifier`.

 You can work around with parentheses:

 (double[string]).init;
 (int[int]).init

Thanks a lot!

Kind regards
Andre

Daniel Kozak <kozzi11 gmail.com> writes:

On Tue, Dec 22, 2020 at 10:15 PM Andre Pany via Digitalmars-d-learn <
digitalmars-d-learn puremagic.com> wrote:

 Hi,

 I am really confused, why is this valid:
 void sample(string[string] s =3D string[string].init){}

 while this causes syntax errors?

 void sample_invalid1(double[string] s =3D double[string].init){}
 void sample_invalid2(int[int] s =3D int[int].init){}

 Kind regards
 Andr=C3=A9

As has been said this is an oddity in the grammar. But why would anyone
need to use this anyway?

  void sample_invalid2(int[int] s =3D int[int].init){}

seems really awful to me anyway.

Steven Schveighoffer <schveiguy gmail.com> writes:

On 12/22/20 5:44 PM, Daniel Kozak wrote:
 On Tue, Dec 22, 2020 at 10:15 PM Andre Pany via Digitalmars-d-learn 
 <digitalmars-d-learn puremagic.com 
 <mailto:digitalmars-d-learn puremagic.com>> wrote:
 
     Hi,
 
     I am really confused, why is this valid:
     void sample(string[string] s = string[string].init){}
 
     while this causes syntax errors?
 
     void sample_invalid1(double[string] s = double[string].init){}
     void sample_invalid2(int[int] s = int[int].init){}
 
     Kind regards
     André
 
 
 As has been said this is an oddity in the grammar. But why would anyone 
 need to use this anyway?
 
    void sample_invalid2(int[int] s = int[int].init){}
 
 seems really awful to me anyway.

Yeah:

void sample_valid(int[int] s = null)

-Steve

Daniel Kozak <kozzi11 gmail.com> writes:

Dne st 23. 12. 2020 1:00 u=C5=BEivatel Steven Schveighoffer via
Digitalmars-d-learn <digitalmars-d-learn puremagic.com> napsal:

 On 12/22/20 5:44 PM, Daniel Kozak wrote:
 On Tue, Dec 22, 2020 at 10:15 PM Andre Pany via Digitalmars-d-learn
 <digitalmars-d-learn puremagic.com
 <mailto:digitalmars-d-learn puremagic.com>> wrote:

     Hi,

     I am really confused, why is this valid:
     void sample(string[string] s =3D string[string].init){}

     while this causes syntax errors?

     void sample_invalid1(double[string] s =3D double[string].init){}
     void sample_invalid2(int[int] s =3D int[int].init){}

     Kind regards
     Andr=C3=A9


 As has been said this is an oddity in the grammar. But why would anyone
 need to use this anyway?

    void sample_invalid2(int[int] s =3D int[int].init){}

 seems really awful to me anyway.

 Yeah:

 void sample_valid(int[int] s =3D null)

 -Steve


Yes AA.init is null per doc.

https://dlang.org/spec/hash-map.html#construction_and_ref_semantic

Andre Pany <andre s-e-a-p.de> writes:

On Wednesday, 23 December 2020 at 07:08:31 UTC, Daniel Kozak 
wrote:
 Dne st 23. 12. 2020 1:00 uživatel Steven Schveighoffer via 
 Digitalmars-d-learn <digitalmars-d-learn puremagic.com> napsal:

 On 12/22/20 5:44 PM, Daniel Kozak wrote:
 [...]

 Yeah:

 void sample_valid(int[int] s = null)

 -Steve


 Yes AA.init is null per doc.

 https://dlang.org/spec/hash-map.html#construction_and_ref_semantic

Thanks for clarification, I was not aware that AA.init is 
technically the same as null.

Kind regards
Andre