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digitalmars.D - Suggestions

reply vincent catrino <catrino cbs.cnrs.fr> writes:
Hi there,

I have been following D for about 1.5 year and I really like this
language. I use it for casual programming and for fun. I'm a
software engineer using mainly C, JAVA and FORTRAN 77.

There are a few things that I use all the time in C and JAVA and
that I really would appreciate to find in the D language.

* C99 allows the following :
int func( int n, int a[n][n] ) {
   ... do something ...
}
D forbids this. It is possible to have this in D for example by
creating a structure like this.
struct Mati {
   int *ptr;
   int dim;
   int *opIndex(int i) { return ptr + i*dim; }
};
and rewriting func like this
int func( int n, int *ptr ) {
   Mati m = new Mati();
   m.ptr = ptr;
   m.dim = n;

   m[1][5] = 3;
}
Would it be possible to have this in D directly ? Or maybe there
is a cute D way to have this already and I woould be glad to learn
it.

* Indirection.
in C when you get a structure pointer you use the '->' operator
instead of '.' to access members. In D only '.' is allowed. Would
it be possible to have '->' too as a synomym for '.' ? This is
just syntaxic sugar and D works well without this but when working
in D I switch back to my C habits and naturally use '->'.

* JAVA has a base object type too which is used as the base class
for all other classes. In JAVA the basic object type provides
synchronization primitives which are quite useful :
void wait()
void wait( long timeout )
void notify()
void notifyAll()
Maybe it is already possible to do this in D and I haven't
understood how. If yes I would be glad to learn how to do so, if
not maybe these facilities might be added to the D object type ?

Best regards

Vincent
Dec 04 2006
next sibling parent Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
vincent catrino wrote:

 Hi there,
 
 I have been following D for about 1.5 year and I really like this
 language. I use it for casual programming and for fun. I'm a
 software engineer using mainly C, JAVA and FORTRAN 77.
 
 There are a few things that I use all the time in C and JAVA and
 that I really would appreciate to find in the D language.
 
 * C99 allows the following :
 int func( int n, int a[n][n] ) {
    ... do something ...
 }
 D forbids this. It is possible to have this in D for example by
 creating a structure like this.
 struct Mati {
    int *ptr;
    int dim;
    int *opIndex(int i) { return ptr + i*dim; }
 };
 and rewriting func like this
 int func( int n, int *ptr ) {
    Mati m = new Mati();
    m.ptr = ptr;
    m.dim = n;
 
    m[1][5] = 3;
 }
 Would it be possible to have this in D directly ? Or maybe there
 is a cute D way to have this already and I woould be glad to learn
 it.


D doesn't have dynamic multidimensional arrays built in (it may be on a 
TODO for >= 2.0). A better way is to consistently use a custom array 
type (just like you do). I.e. something like:

struct SquareMatrix {
   int *ptr;
   int dim;
   int opIndex(int i, int j) { return ptr[j+i*dim]; }
   int opIndexAssign(int v, int i, int j) { return ptr[j+i*dim] = v;}
}

(Or the Mati one above) And pass that directly to the functions:

int func(SquareMatrix m) {
	m[1,5] = 3;
	...
}

I have written several such array and matrix types and they work well in 
practice. The downsides are:

- No reference return type from opIndex, meaning e.g, m[1,5]++; is 
impossible. (You solve that quite neatly)
- Not standardized
- Mixing slicing and indexing not possible with the .. syntax

Regards,

Oskar
Dec 04 2006
prev sibling parent Daniel Keep <daniel.keep+lists gmail.com> writes:
vincent catrino wrote:

 Hi there,


Howdy, and welcome to the NG.  Please keep your arms and legs inside the 
NG at all times, lest you lose them. :P


 * Indirection.
 in C when you get a structure pointer you use the '->' operator
 instead of '.' to access members. In D only '.' is allowed. Would
 it be possible to have '->' too as a synomym for '.' ? This is
 just syntaxic sugar and D works well without this but when working
 in D I switch back to my C habits and naturally use '->'.


Don't hold your breath.  It's a conscious design decision for D to avoid 
having many ways of saying the same thing.  Afraid you'll just have to 
learn to not use '->' any more :3

Look on the bright side: now you only need to remember one member access 
operator!


 * JAVA has a base object type too which is used as the base class
 for all other classes. In JAVA the basic object type provides
 synchronization primitives which are quite useful :
 void wait()
 void wait( long timeout )
 void notify()
 void notifyAll()
 Maybe it is already possible to do this in D and I haven't
 understood how. If yes I would be glad to learn how to do so, if
 not maybe these facilities might be added to the D object type ?


I'm not familiar with what these do, but you might want to take a peek 
at the std.thread module.  It's hard to say much else without knowing 
what those methods do (and I have no intention of learning any more Java 
than I already know.)

	-- Daniel
Dec 04 2006