On 01/03/2013 10:54 PM, Michael wrote:
Thanks guys)
auto With(alias fun, I)(I o) // maybe add a template constraint here
{
static if(isAssignable!(I, typeof(null)))
return o is null ? null : fun(o);
else
return fun(o);
}
foreach(p; persons)
p.With!(x => x.address);
Now if I want add a somewhat task into expression "x => x.address", for
example "writeln(x.address)", a code should be rewritten like
foreach(p; persons)
p.With!(x => {writeln(x.address); return x.address;}());
As I understand, right part of expression above - "{ ... }()" is
anonymous function (or delegate, or closure) that immediately called in
lambda expression. Right? Is right behaviour?
You understand this correctly, but it is a somewhat roundabout way to
achieve what you want to do.
This should work as well:
foreach(p; persons)
p.With!((x){writeln(x.address); return x.address;});
The reason is that there are two different ways for forming function
literals. The lambda literal a=>exp is immediately rewritten to (a){
return exp; }
Historically, the lambda syntax has not been available, turning function
literal heavy code into something that looked like
{return{return(){return((){return}())}. The introduction of '=>' was a
backwards-compatible addition.
