Re: We need to have a way to say "convert this nested function into a struct"

[via Digitalmars-d]

On Saturday, 6 June 2015 at 13:44:51 UTC, Jacob Carlborg wrote:
On 2015-06-06 08:59, Jonathan M Davis wrote:
On Saturday, 6 June 2015 at 06:16:17 UTC, Andrei Alexandrescu 
wrote:
Nested functions that allocate their environment dynamically 
can be
quite useful. However, oftentimes the need is to convert the 
code plus
the data needed into an anonymous struct that copies the 
state inside,
similar to C++ lambdas that capture by value.
I wonder how to integrate that within the language nicely.

Some of us were discussing this at dconf. Essentially, we need 
a way to
create a functor similar to how C++ lambdas do. The most 
straightforward
way would involve string mixins, and you'd do something like

auto f = makeFunctor!"function code here"(arguments);

Which could look like this with AST macros ;)

auto f = makeFunctor(args) {
   function code goes here, no strings are needed
}

Well, this kind of syntax can be implemented without AST macros. 
But there are syntactic ambiguities if the delegate has 
parameters:

auto f = makeFunctor(args) (a, b) { }

Is the second pair of parens the delegate's parameter list, or a 
call a callable object returned by makeFunctor?

Besides, do we require a semicolon after the closing brace? If 
yes, that would be at odds with the rest of the language, but if 
not, we cannot easily chain such calls...