Re: Empty functions
On Thu, Oct 29, 2020 at 09:06:21AM +, Jan Hönig via Digitalmars-d-learn
wrote:
> On Thursday, 29 October 2020 at 09:01:12 UTC, Jan Hönig wrote:
> > This would mean, that this one should work as well.
>
> It does not work as I intended, as `() => {}` has not the return type
> of `void`.
>
> (I don't know how to print: `ReturnType!(() => {})`)
What you want is `() {}`, which is equivalent to `void function() {}`.
`() => {}` means something different; it's equivalent to:
() { return () {}; }
i.e., it's a function that returns an empty function.
T
--
Tell me and I forget. Teach me and I remember. Involve me and I understand. --
Benjamin Franklin
Re: Empty functions
On Thursday, 29 October 2020 at 09:06:21 UTC, Jan Hönig wrote:
On Thursday, 29 October 2020 at 09:01:12 UTC, Jan Hönig wrote:
This would mean, that this one should work as well.
It does not work as I intended, as `() => {}` has not the
return type of `void`.
(I don't know how to print: `ReturnType!(() => {})`)
Arrow lambdas take a single *expression* on the right-hand side,
not a function body between curly braces. When you write
() => {}
the right-hand side is interpreted as an expression, and is
expanded by the compiler to
() => function void() {}
I.e., it is a function that returns another function.
Re: Empty functions
On 29/10/2020 10:06 PM, Jan Hönig wrote:
On Thursday, 29 October 2020 at 09:01:12 UTC, Jan Hönig wrote:
This would mean, that this one should work as well.
It does not work as I intended, as `() => {}` has not the return type of
`void`.
(I don't know how to print: `ReturnType!(() => {})`)
alias RT = void function();
alias Type = RT function();
() => 7;
is equivalent to:
int func() {
return 7;
}
Or:
() { return 7; }
Re: Empty functions
On Thursday, 29 October 2020 at 09:01:12 UTC, Jan Hönig wrote:
This would mean, that this one should work as well.
It does not work as I intended, as `() => {}` has not the return
type of `void`.
(I don't know how to print: `ReturnType!(() => {})`)
Re: Empty functions
On Thursday, 29 October 2020 at 08:48:59 UTC, rikki cattermole
wrote:
() => {}
Is actually:
() => Expression
Rule: ref|opt ParameterWithMemberAttributes => AssignExpression
https://dlang.org/spec/expression.html#lambdas
This would mean, that this one should work as well.
And you can![1]
I have changed line 13 from `F();` to `return F();`.
Why does this help???
This is a little weird.
[1]: https://run.dlang.io/is/eGah5v
Re: Empty functions
(Params){ FunctionBody; }
Rule: ref|opt ParameterWithMemberAttributes FunctionLiteralBody
https://dlang.org/spec/expression.html#function_literals
void function()
Is a type https://dlang.org/spec/type.html#delegates
() => {}
Is actually:
() => Expression
Rule: ref|opt ParameterWithMemberAttributes => AssignExpression
https://dlang.org/spec/expression.html#lambdas
