DMD 0.165 release

[Sean Kelly]

Walter Bright wrote:
> Sean Kelly wrote:
>> Walter Bright wrote:
>>> I was going to call this 1.0 RC1, but I just could not resist adding 
>>> the lazy expression evaluation. This adds one of the big capabilities 
>>> of common lisp.
>>>
>>> http://www.digitalmars.com/d/changelog.html
>>
>> Nice work!  I'm not sure I understand the advantage offered to the 
>> enforcement example however, unless it is in creating the message 
>> string (a benefit that was already demonstrated).  Where is the lazy 
>> evaluation occurring?
> 
> The example has typos in it, but the advantage is to not evaluate the 
> msg (which can be arbitrarily complex) unless an error actually occurs.

Thanks.  I suppose it's worth mentioning that lazy evaluation can result 
in some confusing errors similar to those encountered with macro 
functions vs. normal functions.  For example:

     void fn( char delegate() ch )
     {
         if( ch() == 'c' || ch() == 'd' )
         {
             printf( "match\n" );
         }
     }

     size_t pos = 0;
     char[] buf = "abdc";

     fn( buf[++pos] );

The above code would print "match" because pos would be incremented 
twice.  This makes API changes from the classic to lambda syntax a risky 
venture, as it risks silently breaking once-working code.


Sean