lazy redux

[Denis Koroskin]

On Mon, 07 Dec 2009 16:17:10 +0300, Michal Minich  
<michal.minich at gmail.com> wrote:

> Hello bearophile,
>
>> Michal Minich:
>>
>>> But introduction "{ epx }" as delegate/function literal for functions
>>> with no arguments, which implicitly returns result of the expression,
>>> seems to me as a good idea.
>>>
>> It's a special case, and special cases help to kill languages. It's
>> not important enough.
>> But a general shorter syntax for lambdas is possible, like the C# one.
>> Evaluations lazy arguments only 0 or 1 times sounds like a nice idea.
>> Bye,
>> bearophile
>
> Yes, it works well in C#, and it is one of the best extension of this  
> language (only adding generics was better).
>
> Consider how it works in C#, and how it could in D
>
> // 1. lambda with no parameter  int a;
> var t = new Thread (  () => a=42  );
>
> // 2. lambda with one parameter
> string[] arr;
> Array.FindAll (arr, item => item.Contains ("abc"));
>           // 3. lambda with more parameters
> Foo (  (a, b) => a + b );
>
> // 4. lambda with statement (previous examples were expressions)
> Array.FindAll (arr, item =>  { return item.Contains ("abc"); } );
> // curly braces, semicolon and return are required when statement is  
> used.
>
> D could use:
>
> 1. auto t = new Thread ( { a=42 } );
> or auto t = new Thread ( () { a=42 } );
>

It already works, just try it (but don't forget to put a semicolon at the  
end).

> 2. array.findAll (arr, (item) { item.contains ("abc") } );
> 3. foo ( (a, b) { a + b } );
>
> 4. array.findAll (arr, (item) { return item.contains ("abc"); } );
>
> I'm not proposing this syntax (maybe I probably should, but I have  
> feeling I would not be first). It may not even be possible to parse it,  
> but seems to me more similar to how currently functions are written. In  
> this setting {exp} or {stm} is not *special* case.
>
>

I believe it would work. And yes, it was already proposed by many others.