With new c# 7 tuple syntax, is it possible to specify a lambda with a tuple as parameter and use unpacked values inside the lambda?
Example:
var list = new List<(int,int)>();
normal way to use a tuple in lambda:
list.Select(value => value.Item1*2 + value.Item2/2);
i expected some new sugar to avoid .Item1 .Item2, like:
list.Select((x,y) => x*2 + y/2);
The last line does not work because it is treated as two parameters for lambda. I am not sure if there is a way to do it actually.
EDIT:
I tried double parentesis in lambda definition and it didn't work: ((x,y)) => ..., and maybe it was stupid to try, but double parenthesis actually work here:
list.Add((1,2));
Also, my question is not quite about avoiding ugly default names .Item .Item2, it is about actual unpacking a tuple in lambda (and maybe why it's not implemented or not possible). If you came here for a solution to default names, read Sergey Berezovskiy's answer.
EDIT 2:
Just thought of a more general use case: is it possible (or why not) to "deconstruct" tuple passed to a method? Like this:
void Foo((int,int)(x,y)) { x+y; }
Instead of this:
void Foo((int x,int y) value) { value.x+value.y }
Answer
As you have observed, for:
var list = new List<(int,int)>();
One would at least expect to be able to do the following:
list.Select((x,y) => x*2 + y/2);
But the C# 7 compiler doesn't (yet) support this. It is also reasonable to desire sugar that would allow the following:
void Foo(int x, int y) => ...
Foo(list[0]);
with the compiler converting Foo(list[0]); to Foo(list[0].Item1, list[0].Item2); automatically.
Neither of these is currently possible. However, the issue, Proposal: Tuple deconstruction in lambda argument list, exists on the dotnet/csharplang repo on GitHub, requesting that the language team consider these features for a future version of C#. Please do add your voices to that thread if you too would like to see support for this.