typedef

[Tim M]

On Sat, 07 Mar 2009 17:04:56 +1300, Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org> wrote:

> Tim M wrote:
>> On Sat, 07 Mar 2009 06:47:40 +1300, Andrei Alexandrescu  
>> <SeeWebsiteForEmail at erdani.org> wrote:
>>
>>> I tried typedef in two instances, to sadly conclude that it's not  
>>> useful as a true abstraction mechanism. The good news is that it's  
>>> very close to being useful.
>>  I've never really found typedefs of any use. You say it makes it  
>> clearer that you are dealing with IDType objects. But they are not  
>> objects. If you had used objects you could have defined the constuctor  
>> to get the syntax you are looking for because taking away this syntax:
>>  IDType id = 5;
>>  Should also remove the following syntaxes to keep D simple:
>>  *=
>> +=
>> -+
>> %=
>>  etc..
>>   So you end up with a type that stores int data but cant be used for  
>> arithmetic. What good would that be keeping in mind that D already has  
>> enums?
>
> Well I was wondering whether others have success stories about typedef  
> to share. Here's an example that would have made it very handy for me to  
> use a good typedef.
>
> I have a machine translation app that deals with sentences in two  
> languages. Furthermore, in the target language there are several  
> hypotheses per sentence. I undergo intensive manipulation of these  
> things, and found bugs because I confuse e.g. the IDs of sentences in  
> different languages. So I index in a hash for one language with an ID  
> from another language, which is a bug.
>
> So I though, alright, let me typedef IDs so they never mix up:
>
> typedef uint SourceSntID;
> typedef uint TargetSntID;
> typedef uint HypothesisID;
>
> Things did improve considerably but I found it annoying that these IDs,  
> which are supposed to be essentially independent types, convert to and  
> from uint at the drop of a hat. I could define structs for them but  
> that's onerous - like dozens of lines instead of one line.
>
>
> Andrei


Derelict uses typedef for functions and alias for others by convention:
"The declarations of the function pointers should be typedefed and should  
have the following syntax:"
http://svn.dsource.org/projects/derelict/trunk/docs/derelictify.html

It seems to be in strong use for where an alias could do the job just fine:
http://www.google.com/search?rls=en&rls=en&q=site:dsource.org+typedef&sourceid=opera&ie=utf-8&oe=utf-8