Reddit: why aren't people using D?

[Steven Schveighoffer]

On Mon, 27 Jul 2009 10:54:00 -0400, Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org> wrote:

>
>> That's why properties are not
>> functions.
>
> This post had a negative effect on me: I now think properties are  
> functions even more than before.

Let me bring you back to the issue at hand:

writefln = "hi";

:)

properties are *implemented* using functions, but both properties and  
function usage should be restricted to disallow bizare code.

Another example:

I've brought up this example before, but I'll summarize the issue.  I  
created a TimeSpan struct for Tango, which represents a span of time.  I  
had static functions to create time spans, and properties to convert time  
spans.  For example:

struct TimeSpan
{
   static TimeSpan seconds(long n); // returns a TimeSpan representing n  
seconds

   ...

   long seconds(); // convert this timespan to seconds
}

So you use it like this:

auto ts = TimeSpan.seconds(5);
assert ts.seconds == 5;

But then I got a bug report one day that this assert fails:

auto ts = TimeSpan.seconds(5);
ts.seconds = 4;
assert(ts.seconds == 4);

What the second line does is create a temporary TimeSpan of 4 seconds, and  
throw it away.

What happened here?  Why did the compiler compile this code at all?  Well,  
because I can't tell the compiler "no, that static seconds function is  
*not* a property", someone tried to use it as one, and then complained it  
didn't work like it should.  Would anyone reading the second line of code,  
knowing it compiles, *not* think "aha! TimeSpan has a way to set it's  
seconds component"?

The "solution" was to rename the static function to fromSeconds, although  
this is still valid code:

ts.fromSeconds = 4;

it doesn't look like it means anything (what's this fromSeconds field?).   
But WTF?  Why do I have to do this kind of shit instead of just telling  
the compiler "this is how you use my object.  Any other uses are invalid.   
End of discussion".

For reference: http://www.dsource.org/projects/tango/ticket/1184

-Steve