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digitalmars.D.learn - defining in a module symbols for export

reply spir <denis.spir gmail.com> writes:
Hello,

Let us say I have a parsing library. Now, I want to define parsers in stand=
-alone modules -- for code structuration and reusability. Then, import them=
 from apps that need them.
Is there another way than defining the parser (=3D=3D list of patterns) at =
the module's top-level. I have nothing against this, since the module is de=
dicated to this anyway -- but dmd refuses.
More generally, I find myself unable to define structured objects at a modu=
les's top level. for instancz:

=3D=3D=3D mod.d =3D=3D
import std.stdio;

struct S {
    int i;
    void speak() {writeln("i: ",this.i);}
}
=3D=3D=3D __trials__.d =3D=3D=3D
import mod;

auto s =3D S();
s.speak();
s.i =3D 1;
writeln(s.i);

void main () {
}

=3D=3D=3D compilation =3D=3D=3D
__trials__.d(19): no identifier for declarator s.speak
__trials__.d(20): no identifier for declarator s.i
__trials__.d(21): found '.' when expecting ')'
__trials__.d(21): semicolon expected, not 'i'
__trials__.d(21): no identifier for declarator i
__trials__.d(21): semicolon expected, not ')'
__trials__.d(21): Declaration expected, not ')'

Why does dmd refuse? If I put the code in a function, I can compile, link, =
and run it. But this does not match my use case: I need to export symbols (=
patterns) defined there; so, i guess, they must be defined at the top of th=
e module. Is there another solution?

I take the opportunity to ask whether it is possible to define which symbol=
s are to be _ex_ported.


Denis
-- -- -- -- -- -- --
vit esse estrany =E2=98=A3

spir.wikidot.com
Nov 22 2010
next sibling parent reply bearophile <bearophileHUGS lycos.com> writes:
spir:


 More generally, I find myself unable to define structured objects at a
modules's top level. for instancz:


I suggest to declare global variables and then initialize them in a "static
this() {...}". But generally I suggest you to minimize the number of global
variables.

Bye,
bearophile
Nov 22 2010
parent spir <denis.spir gmail.com> writes:
On Mon, 22 Nov 2010 15:11:29 -0500
bearophile <bearophileHUGS lycos.com> wrote:


 spir:
=20

 More generally, I find myself unable to define structured objects at a =




modules's top level. for instancz:

=20
 I suggest to declare global variables and then initialize them in a "stat=


ic this() {...}". But generally I suggest you to minimize the number of glo=
bal variables.

=20
 Bye,
 bearophile


Yes, I would generally agree (I normally have about nothing at module tople=
vel), but then how can they be exported? A parser module is precisely here =
to define symbols for export... How do you guys write that?


denis
-- -- -- -- -- -- --
vit esse estrany =E2=98=A3

spir.wikidot.com
Nov 22 2010
prev sibling next sibling parent reply =?UTF-8?B?UGVsbGUgTcOlbnNzb24=?= <pelle.mansson gmail.com> writes:
On 11/22/2010 08:18 PM, spir wrote:

 Hello,

 Let us say I have a parsing library. Now, I want to define parsers in
stand-alone modules -- for code structuration and reusability. Then, import
them from apps that need them.
 Is there another way than defining the parser (== list of patterns) at the
module's top-level. I have nothing against this, since the module is dedicated
to this anyway -- but dmd refuses.
 More generally, I find myself unable to define structured objects at a
modules's top level. for instancz:

 === mod.d ==
 import std.stdio;

 struct S {
      int i;
      void speak() {writeln("i: ",this.i);}
 }
 === __trials__.d ===
 import mod;

 auto s = S();
 s.speak();
 s.i = 1;
 writeln(s.i);

 void main () {
 }

 === compilation ===
 __trials__.d(19): no identifier for declarator s.speak
 __trials__.d(20): no identifier for declarator s.i
 __trials__.d(21): found '.' when expecting ')'
 __trials__.d(21): semicolon expected, not 'i'
 __trials__.d(21): no identifier for declarator i
 __trials__.d(21): semicolon expected, not ')'
 __trials__.d(21): Declaration expected, not ')'

 Why does dmd refuse? If I put the code in a function, I can compile, link, and
run it. But this does not match my use case: I need to export symbols
(patterns) defined there; so, i guess, they must be defined at the top of the
module. Is there another solution?

 I take the opportunity to ask whether it is possible to define which symbols
are to be _ex_ported.


 Denis
 -- -- -- -- -- -- --
 vit esse estrany ☣

 spir.wikidot.com


To initialize at runtime:

     S s;
     static this() {
         s.i = 1;
     }

to initialize at compile time:

     S getS() { S s; s.i = 1; return s; }
     S s = getS();

Use public/private to control which symbols are availible. 
Unfortunately, this doesn't really work at the moment :-)
Nov 22 2010
parent spir <denis.spir gmail.com> writes:
On Mon, 22 Nov 2010 22:17:46 +0100
Pelle M=C3=A5nsson <pelle.mansson gmail.com> wrote:


 On 11/22/2010 08:18 PM, spir wrote:

 Hello,

 Let us say I have a parsing library. Now, I want to define parsers in s=




tand-alone modules -- for code structuration and reusability. Then, import =
them from apps that need them.

 Is there another way than defining the parser (=3D=3D list of patterns)=




 at the module's top-level. I have nothing against this, since the module i=
s dedicated to this anyway -- but dmd refuses.

 More generally, I find myself unable to define structured objects at a =




modules's top level. for instancz:

 =3D=3D=3D mod.d =3D=3D
 import std.stdio;

 struct S {
      int i;
      void speak() {writeln("i: ",this.i);}
 }
 =3D=3D=3D __trials__.d =3D=3D=3D
 import mod;

 auto s =3D S();
 s.speak();
 s.i =3D 1;
 writeln(s.i);

 void main () {
 }

 =3D=3D=3D compilation =3D=3D=3D
 __trials__.d(19): no identifier for declarator s.speak
 __trials__.d(20): no identifier for declarator s.i
 __trials__.d(21): found '.' when expecting ')'
 __trials__.d(21): semicolon expected, not 'i'
 __trials__.d(21): no identifier for declarator i
 __trials__.d(21): semicolon expected, not ')'
 __trials__.d(21): Declaration expected, not ')'

 Why does dmd refuse? If I put the code in a function, I can compile, li=




nk, and run it. But this does not match my use case: I need to export symbo=
ls (patterns) defined there; so, i guess, they must be defined at the top o=
f the module. Is there another solution?

 I take the opportunity to ask whether it is possible to define which sy=




mbols are to be _ex_ported.

 Denis
 -- -- -- -- -- -- --
 vit esse estrany =E2=98=A3

 spir.wikidot.com


=20
 To initialize at runtime:
=20
      S s;
      static this() {
          s.i =3D 1;
      }
=20
 to initialize at compile time:
=20
      S getS() { S s; s.i =3D 1; return s; }
      S s =3D getS();
=20
 Use public/private to control which symbols are availible.=20
 Unfortunately, this doesn't really work at the moment :-)


Thank you very much!
Unfortunately, a parser is typically a bunch a definitions. I cannot expect=
 the user (first, myself) to write a func for every little setting needed.
I could write setters on classes that require the user to set attributes, b=
ut as shown in the example, method calls are also refused.
Where is the issue, actually?


Denis
-- -- -- -- -- -- --
vit esse estrany =E2=98=A3

spir.wikidot.com
Nov 23 2010
prev sibling parent reply Jesse Phillips <jessekphillips+D gmail.com> writes:
spir Wrote:



 === mod.d ==
 import std.stdio;
 
 struct S {
     int i;
     void speak() {writeln("i: ",this.i);}
 }
 === __trials__.d ===
 import mod;
 
 auto s = S();
 s.speak();
 s.i = 1;
 writeln(s.i);
 
 void main () {
 }


Others have answered how to initialize variables, but haven't explained the
compilation error. A simple example of what you are doing wrong is:

import std.stdio;

writeln("foo");

void main () {
}

How are you to execute writeln()? You probably wouldn't try this under normal
conditions, but is what you are trying to do. You can place it in a static this
constructor:

import std.stdio;

static this() { writeln("foo"); }

void main () {
}

Note you can move the calls into main and it compiles fine:

void main () {
s.speak();
s.i = 1;
writeln(s.i);
}
Nov 22 2010
parent spir <denis.spir gmail.com> writes:
On Mon, 22 Nov 2010 16:20:07 -0500
Jesse Phillips <jessekphillips+D gmail.com> wrote:


 spir Wrote:
=20
=20

 =3D=3D=3D mod.d =3D=3D
 import std.stdio;
=20
 struct S {
     int i;
     void speak() {writeln("i: ",this.i);}
 }
 =3D=3D=3D __trials__.d =3D=3D=3D
 import mod;
=20
 auto s =3D S();
 s.speak();
 s.i =3D 1;
 writeln(s.i);
=20
 void main () {
 }


=20
 Others have answered how to initialize variables, but haven't explained t=


he compilation error. A simple example of what you are doing wrong is:

=20
 import std.stdio;
=20
 writeln("foo");
=20
 void main () {
 }
=20
 How are you to execute writeln()? You probably wouldn't try this under no=


rmal conditions, but is what you are trying to do. You can place it in a st=
atic this constructor:

=20
 import std.stdio;
=20
 static this() { writeln("foo"); }
=20
 void main () {
 }
=20
 Note you can move the calls into main and it compiles fine:
=20
 void main () {
 s.speak();
 s.i =3D 1;
 writeln(s.i);
 }
=20


Right. Seems I may put the whole parser definition into static this(). I'll=
 try it. Will work if symbols defined in there are available for export.


Denis
-- -- -- -- -- -- --
vit esse estrany =E2=98=A3

spir.wikidot.com
Nov 23 2010