Re: lambda syntax with curly braces

[bachmeier via Digitalmars-d-learn]

On Monday, 10 August 2015 at 15:05:55 UTC, sigod wrote:
I see. But it's really counter intuitive after working with C#. 
Probably documentation should stress out the difference.


Thanks, Adam.


I assume you mean this page:

http://dlang.org/expression.html

There's an Improve this page button in the upper right corner. 
It's very easy to recommend a change.

Re: lambda syntax with curly braces

[sigod via Digitalmars-d-learn]

On Monday, 10 August 2015 at 16:02:31 UTC, bachmeier wrote:

On Monday, 10 August 2015 at 15:05:55 UTC, sigod wrote:
I see. But it's really counter intuitive after working with 
C#. Probably documentation should stress out the difference.


Thanks, Adam.


I assume you mean this page:

http://dlang.org/expression.html

There's an Improve this page button in the upper right 
corner. It's very easy to recommend a change.


Good point.

But I seldom do this because English isn't my native language.

Re: lambda syntax with curly braces

[bachmeier via Digitalmars-d-learn]

On Monday, 10 August 2015 at 16:15:40 UTC, sigod wrote:


Good point.

But I seldom do this because English isn't my native language.


Your English looks fine to me. Close enough to native that I 
can't tell the difference.

Re: lambda syntax with curly braces

[sigod via Digitalmars-d-learn]

On Monday, 10 August 2015 at 14:05:30 UTC, Adam D. Ruppe wrote:

On Monday, 10 August 2015 at 13:57:50 UTC, sigod wrote:

[...]


It does exactly what that says: rewrites it to

(a) {
  return {
   writeln(a);
  };
}


which is returning a delegate.


[...]


So your code passed a delegate that returned a delegate to 
each. Since the one returned wasn't called, the writeln never 
happened.


If you call it like so:

[1,2,3,4,5]
.each!(a = {
writeln(a);
}()); // added parens call the returned delegate

then you see it.




The = thing in D is meant only for trivial, single line 
things. If you want multiple lines, that's where the {} syntax 
comes in with no need for the =.


.each!( (a) {
   writeln(a);
  });


I see. But it's really counter intuitive after working with C#. 
Probably documentation should stress out the difference.


Thanks, Adam.

lambda syntax with curly braces

[sigod via Digitalmars-d-learn]

From docs:
The following part = AssignExpression is rewritten to 
FunctionLiteralBody:

{ return AssignExpression ; }


So, I wonder what happens when curly braces already in place?

Consider this example:
```
import std.algorithm;
import std.stdio;

void main() {
[1,2,3,4,5]
.each!(a = { // remove `=` and you'll get output
writeln(a);
});
}
```

This code compiles and doesn't output anything. Which is very 
counterintuitive for me, because my main experience with lambdas 
was in C#. Where it's perfectly fine to write `identifiers = { 
/* some code */ }`.

Re: lambda syntax with curly braces

[Adam D. Ruppe via Digitalmars-d-learn]

On Monday, 10 August 2015 at 13:57:50 UTC, sigod wrote:

From docs:
The following part = AssignExpression is rewritten to 
FunctionLiteralBody:

{ return AssignExpression ; }


So, I wonder what happens when curly braces already in place?


It does exactly what that says: rewrites it to

(a) {
  return {
   writeln(a);
  };
}


which is returning a delegate.


This code compiles and doesn't output anything.


So your code passed a delegate that returned a delegate to each. 
Since the one returned wasn't called, the writeln never happened.


If you call it like so:

[1,2,3,4,5]
.each!(a = {
writeln(a);
}()); // added parens call the returned delegate

then you see it.




The = thing in D is meant only for trivial, single line things. 
If you want multiple lines, that's where the {} syntax comes in 
with no need for the =.


.each!( (a) {
   writeln(a);
  });