I bask originally this qustion in this thread :
http://forum.dlang.org/post/rsnswykpjfzenplivkhm@forum.dlang.org

but another thread is better as that is not exactly same topic.


I would like to use custom annotate/attribute on members as:


struct A
{
        @Parser(
                 start = "( word ) =>  word[0] == '>'",
                 end   = "( word ) =>  word[0] == '\n'" )
        string header;

}


but it seem we can't use curstom annotation in D and mxin in this
case are not easy.

This custom attribute is a metadata to explain how to retrieve
this field from a file. This will aloow to create a global parser
and give to this parrser data structure to get back.
Parser could to b an input range were
hront give currentfilled  struct and popfront will look foward in
buffer given by file.byChunk() using this metadata.
When all field are filled give the instance to front …

On Friday, 23 May 2014 at 15:17:52 UTC, bioinfornatics wrote:
> I bask originally this qustion in this thread :
> http://forum.dlang.org/post/rsnswykpjfzenplivkhm@forum.dlang.org
>
> but another thread is better as that is not exactly same topic.
>
>
> I would like to use custom annotate/attribute on members as:
>
>
> struct A
> {
>         @Parser(
>                  start = "( word ) =>  word[0] == '>'",
>                  end   = "( word ) =>  word[0] == '\n'" )
>         string header;
>
> }
>
>
> but it seem we can't use curstom annotation in D and mxin in this
> case are not easy.
>
> This custom attribute is a metadata to explain how to retrieve
> this field from a file. This will aloow to create a global parser
> and give to this parrser data structure to get back.
> Parser could to b an input range were
> hront give currentfilled  struct and popfront will look foward in
> buffer given by file.byChunk() using this metadata.
> When all field are filled give the instance to front …

Sorry for typos they are severals.


So to continue te code below is more close to D but do not build:

import std.stdio;

struct attribute { }

@attribute
struct section {
     bool delegate( string ) start;
     bool delegate( string ) end;

     this( in bool delegate( string ) start, in bool delegate(
string ) end)
     {
         this.start  = start,
         this.end    = end;
     }
}


struct A {
         @section( ( word ) =>  word[0] == '@', ( word ) =>
word[0] == '\n')
         int a;
}


int main(string[] args)
{
     A a;
     return 0;
}


testCustomAttributes.d(43): Error: delegate
testCustomAttributes.A.__lambda2!(string).__lambda2 function
literals cannot be class members

On 05/23/2014 09:09 AM, bioinfornatics wrote:

> struct A {
>           @section( ( word ) =>  word[0] == '@', ( word ) =>
> word[0] == '\n')
>           int a;
> }

I was able to make that work if I used function instead of delegate:

import std.stdio;

struct attribute { }

alias MatchFunc = bool function( string );

@attribute
struct section {
     MatchFunc start;
     MatchFunc end;

     this( in MatchFunc start,
           in MatchFunc end)
     {
         this.start  = start,
         this.end    = end;
     }
}

struct A {
    @section((string word) => word[0] == '@',
             (string word) => word[0] == '\n')
    int a;
}

import std.traits;

void main()
{
    auto aa = A();
    auto t = __traits(getAttributes, A.a);

    foreach (sect; t) {
        auto start_result = sect.start("@test");
        auto end_result = sect.end("\n");

        writefln("Results: %s and %s", start_result, end_result);
    }
}

Ali

On Monday, 26 May 2014 at 19:50:29 UTC, Ali Çehreli wrote:
> On 05/23/2014 09:09 AM, bioinfornatics wrote:
>
> > struct A {
> >           @section( ( word ) =>  word[0] == '@', ( word ) =>
> > word[0] == '\n')
> >           int a;
> > }
>
> I was able to make that work if I used function instead of delegate:
>
> import std.stdio;
>
> struct attribute { }
>
> alias MatchFunc = bool function( string );
>
> @attribute
> struct section {
>      MatchFunc start;
>      MatchFunc end;
>
>      this( in MatchFunc start,
>            in MatchFunc end)
>      {
>          this.start  = start,
>          this.end    = end;
>      }
> }
>
> struct A {
>     @section((string word) => word[0] == '@',
>              (string word) => word[0] == '\n')
>     int a;
> }
>
> import std.traits;
>
> void main()
> {
>     auto aa = A();
>     auto t = __traits(getAttributes, A.a);
>
>     foreach (sect; t) {
>         auto start_result = sect.start("@test");
>         auto end_result = sect.end("\n");
>
>         writefln("Results: %s and %s", start_result, end_result);
>     }
> }
>
> Ali

thanks Ali nice works as usual :-)

it seem delegate will be suppoted into dmdfe 2.066