• Daniel Davidson (32/32) Sep 12 2013 Is there any way to simulate the cascade operator (..) of Dart in
• bearophile (8/21) Sep 12 2013 Replacing Dart with D seems quite strange, such two languages
• Daniel Davidson (34/55) Oct 07 2013 The problem with with is the name can not hide each other, so it

"Daniel Davidson" <nospam spam.com> writes:

Is there any way to simulate the cascade operator (..) of Dart in 
D? This operator makes fluid initialization simple.

I am using Dart for code generation but would like to consider D 
if I can find a convenient replacement for the following 
declarative style:

     var dateRange = struct('date_range')
       ..doc = 'Basic pair of start and end dates'
       ..unitTest = true
       ..publicSection = true
       ..members = [
         member('start_date')
         ..type = 'Date',
         member('end_date')
         ..type = 'Date',
       ];

So struct is a function that returns an instance of Struct.

     class Struct extends Decls {
       ...
       /// Documentation for this D struct
       String doc;
       /// List of members of this class
       List<Member> members = [];
       bool unitTest = false;
       ...
     }

..doc = ... assigns to the Struct.doc field and returns the 
original Struct instance so that ..unitTest = true can be applied 
to the original Struct instance, etc.

What is the best way to achieve simple declarative style for very 
large initialization objects?

Thanks,
Dan

"bearophile" <bearophileHUGS lycos.com> writes:

Daniel Davidson:

 I am using Dart for code generation but would like to consider 
 D if I can find a convenient replacement for the following 
 declarative style:

Replacing Dart with D seems quite strange, such two languages 
have so much different usage niches.


     var dateRange = struct('date_range')
       ..doc = 'Basic pair of start and end dates'
       ..unitTest = true
       ..publicSection = true
       ..members = [
         member('start_date')
         ..type = 'Date',
         member('end_date')
         ..type = 'Date',
       ];

A similar syntax is not allowed in D, but there are two things 
that help for this: the C-style initialization of structs, that 
support field names too, and the with(){} statement.

Bye,
bearophile

"Daniel Davidson" <nospam spam.com> writes:

On Thursday, 12 September 2013 at 19:41:49 UTC, bearophile wrote:
 Daniel Davidson:

 I am using Dart for code generation but would like to consider 
 D if I can find a convenient replacement for the following 
 declarative style:

 Replacing Dart with D seems quite strange, such two languages 
 have so much different usage niches.


    var dateRange = struct('date_range')
      ..doc = 'Basic pair of start and end dates'
      ..unitTest = true
      ..publicSection = true
      ..members = [
        member('start_date')
        ..type = 'Date',
        member('end_date')
        ..type = 'Date',
      ];

 A similar syntax is not allowed in D, but there are two things 
 that help for this: the C-style initialization of structs, that 
 support field names too, and the with(){} statement.

 Bye,
 bearophile

The problem with with is the name can not hide each other, so it 
is easy to get into trouble. With C-style initialization I don't 
think you can use as expression - I think you need an lvalue for 
each and this hurts nesting.

I have a style I'm playing with and if anyone has comments or 
improvements (i.e. make more succinct/readable) it would be 
appreciated.

Here is a sample and the source for this and comparable Dart are 
in the links.

     auto d = make((ref Dossier _) {
       _.family = [
        "father" : make((ref Person _) {
            _.birthDate = "2001/1/1";
            _.deathDate = "2101/1/1";
            _.retirementDate = "2100/1/1"; }),
        "mother" : make((ref Person _) {
            _.birthDate = "2005/1/1";
            _.deathDate = "2125/1/1";
            _.retirementDate = "2100/1/1"; }),
        ];
       _.assets = [
        "house" : make((ref Asset _) {
            _.name = "Home on the Hill";
            _.unitValue = 120_000; }),
        "car" : make((ref Asset _) {
            _.name = "Dodge Dart";
            _.unitValue = 500; })
       ];
     });

http://pastebin.com/iLVL20Bz
http://pastebin.com/mLcWDACm

Thanks
Dan