• tcak (22/22) Nov 17 2019 I started working on a project which contains many classes in it.
• Alexandru Ermicioi (15/37) Nov 17 2019 The problem was that module name was same as class name, and that
• Alexandru Ermicioi (7/8) Nov 17 2019 D module can be thought in terms of Java as a public class that
• Adam D. Ruppe (6/8) Nov 17 2019 I'm of the opinion that you should basically never write
• Walter Bright (3/21) Nov 17 2019 The usual D practice is to call the module "spaceposition.d" that contai...

tcak <tcak gmail.com> writes:

I started working on a project which contains many classes in it. 
One of them is name "SpacePosition" which holds x and y position, 
and a method "distance". Distance is defined as both instance 
method and class method. So I can call it like,

SpacePosition.distance( pos1, pos2 );

After defining many classes in the my main.d file, I wanted to 
separate the classes into separate files. I created a new file 
with the name "SpacePosition.d" and put the class into it.

In the main.d, I added the line "import SpacePosition;". And when 
I compile the main.d, BAM!

Error: undefined identifier distance in module SpacePosition

So you have to import it like "import SpacePosition: 
SpacePosition;" or call the method like 
"SpacePosition.Spaceposition.distance( pos1, pos2 )".

While the main purpose of modules/namespaces is to separate the 
things so they can be managed much easily, this adds the code 
weirdness.

I think it would be better to add "import" mechanism a new syntax 
to make calls as done in Java. Example:

import class my.project.classes.SpacePosition;

So the compiler would enforce SpacePosition.d file to contain a 
single class definition with name "SpacePosition".

Alexandru Ermicioi <alexandru.ermicioi gmail.com> writes:

On Sunday, 17 November 2019 at 09:03:03 UTC, tcak wrote:
 I started working on a project which contains many classes in 
 it. One of them is name "SpacePosition" which holds x and y 
 position, and a method "distance". Distance is defined as both 
 instance method and class method. So I can call it like,

 SpacePosition.distance( pos1, pos2 );

 After defining many classes in the my main.d file, I wanted to 
 separate the classes into separate files. I created a new file 
 with the name "SpacePosition.d" and put the class into it.

 In the main.d, I added the line "import SpacePosition;". And 
 when I compile the main.d, BAM!

 Error: undefined identifier distance in module SpacePosition

 So you have to import it like "import SpacePosition: 
 SpacePosition;" or call the method like 
 "SpacePosition.Spaceposition.distance( pos1, pos2 )".

 While the main purpose of modules/namespaces is to separate the 
 things so they can be managed much easily, this adds the code 
 weirdness.

 I think it would be better to add "import" mechanism a new 
 syntax to make calls as done in Java. Example:

 import class my.project.classes.SpacePosition;

 So the compiler would enforce SpacePosition.d file to contain a 
 single class definition with name "SpacePosition".

The problem was that module name was same as class name, and that 
got into conflict. Try make it lowercase then it should work. 
Also check https://dlang.org/dstyle.html for D code style, per 
it's recommendation module name should be all lowercase alpha 
numeric name if possible.

Regarding java like semantics for modules, I doubt it will be 
appropriate since unlike java, D modules repesents a collection 
of interdependent entities (classes, funcs etc.) which sometime 
need access to private state of each other similar to how class 
friends in c++ works, therefore it will be quite complicated to 
expose two classes that are interdependent (access private state 
of each other) if only one is allowed to be public.

Best regards,
Alexandru.

Alexandru Ermicioi <alexandru.ermicioi gmail.com> writes:

On Sunday, 17 November 2019 at 11:36:47 UTC, Alexandru Ermicioi 
wrote:
 ...

D module can be thought in terms of Java as a public class that 
contains a set of nested classes & methods, some public some 
private, with same access rules in between them.

Best regards,
Alexandru.

Adam D. Ruppe <destructionator gmail.com> writes:

On Sunday, 17 November 2019 at 09:03:03 UTC, tcak wrote:
 In the main.d, I added the line "import SpacePosition;". And 
 when I compile the main.d, BAM!

I'm of the opinion that you should basically never write 
single-name modules too, since the module namespace is global.

If it was `myproject.SpacePosition` you'd be fine on this and it 
would protect you from other potential conflicts down the line 
too.

Walter Bright <newshound2 digitalmars.com> writes:

On 11/17/2019 1:03 AM, tcak wrote:
 I started working on a project which contains many classes in it. One of them
is 
 name "SpacePosition" which holds x and y position, and a method "distance". 
 Distance is defined as both instance method and class method. So I can call it 
 like,
 
 SpacePosition.distance( pos1, pos2 );
 
 After defining many classes in the my main.d file, I wanted to separate the 
 classes into separate files. I created a new file with the name 
 "SpacePosition.d" and put the class into it.
 
 In the main.d, I added the line "import SpacePosition;". And when I compile
the 
 main.d, BAM!
 
 Error: undefined identifier distance in module SpacePosition
 
 So you have to import it like "import SpacePosition: SpacePosition;" or call
the 
 method like "SpacePosition.Spaceposition.distance( pos1, pos2 )".

The usual D practice is to call the module "spaceposition.d" that contains 
"SpacePosition".