Creating tuples and returning them from functions is trivial in D:

auto getTuple() { return tuple("Bob", 42); }

but using them afterwards can be confusing and error prone

auto t = getTuple();
writeln("name is ", t[0], " age is ", t[1]);

I really missed the ML syntax to write

let (name, age) = getTuple();

Turns out this is ridiculously easy to implement in D, so here's my very tiny module for this:

https://bitbucket.org/infognition/dstuff/src (scroll down to letassign.d)

It allows you to write:

int x, y, z, age;
string name;

let (name, age) = getTuple();           // tuple
let (x,y,z) = argv[1..4].map!(to!int);  // lazy range
let (x,y,z) = [1,2,3];                  // array

SomeStruct s;
let (s.a, s.b) = tuple(3, "piggies");

If a range or array doesn't have enough elements, this thing will throw, and if it's not desired there's
let (x,y,z)[] = ...
variant that uses just the available data and keeps the rest variables unchanged.

On Thursday, 19 February 2015 at 04:38:32 UTC, thedeemon wrote:
> Creating tuples and returning them from functions is trivial in D:
>
> auto getTuple() { return tuple("Bob", 42); }
>
> but using them afterwards can be confusing and error prone
>
> auto t = getTuple();
> writeln("name is ", t[0], " age is ", t[1]);
>
> I really missed the ML syntax to write
>
> let (name, age) = getTuple();
>
> Turns out this is ridiculously easy to implement in D, so here's my very tiny module for this:
>
> https://bitbucket.org/infognition/dstuff/src (scroll down to letassign.d)
>
> It allows you to write:
>
> int x, y, z, age;
> string name;
>
> let (name, age) = getTuple();           // tuple
> let (x,y,z) = argv[1..4].map!(to!int);  // lazy range
> let (x,y,z) = [1,2,3];                  // array
>
> SomeStruct s;
> let (s.a, s.b) = tuple(3, "piggies");
>
> If a range or array doesn't have enough elements, this thing will throw, and if it's not desired there's
> let (x,y,z)[] = ...
> variant that uses just the available data and keeps the rest variables unchanged.

That's pretty neat! May I turn this code into a d-idioms? Name and link will be kept of course.

On Thursday, 19 February 2015 at 04:38:32 UTC, thedeemon wrote:
> let (name, age) = getTuple();

Maybe change the name to tie:

http://www.cplusplus.com/reference/tuple/tie/

?

Ola Fosheim Grøstad:

> Maybe change the name to tie:
>
> http://www.cplusplus.com/reference/tuple/tie/
>
> ?

I prefer "let", it's much more traditional and descriptive. C++ standard library is often a bad example to follow...

Bye,
bearophile

On Thursday, 19 February 2015 at 09:31:59 UTC, ponce wrote:

> That's pretty neat! May I turn this code into a d-idioms? Name and link will be kept of course.

Sure, if you wish. There was just one person using this thing until today, so I dunno whether it deserves to be in that list.

On Thursday, 19 February 2015 at 09:46:13 UTC, Ola Fosheim Grøstad wrote:
> On Thursday, 19 February 2015 at 04:38:32 UTC, thedeemon wrote:
>> let (name, age) = getTuple();
>
> Maybe change the name to tie:
> http://www.cplusplus.com/reference/tuple/tie/
> ?

SML, OCaml, Haskell, F#, ATS, Rust, Swift and others have it as "let" keyword, so personally I'd prefer continuing that tradition.

On Thursday, 19 February 2015 at 09:50:25 UTC, bearophile wrote:
> I prefer "let", it's much more traditional and descriptive. C++ standard library is often a bad example to follow...

Doesn't "let" normally declare a new variable?

On Thursday, 19 February 2015 at 04:38:32 UTC, thedeemon wrote:
> Creating tuples and returning them from functions is trivial in D:
>
> auto getTuple() { return tuple("Bob", 42); }
>
> but using them afterwards can be confusing and error prone
>
> auto t = getTuple();
> writeln("name is ", t[0], " age is ", t[1]);
>
> I really missed the ML syntax to write
>
> let (name, age) = getTuple();
>
> Turns out this is ridiculously easy to implement in D, so here's my very tiny module for this:
>
> https://bitbucket.org/infognition/dstuff/src (scroll down to letassign.d)
>
> It allows you to write:
>
> int x, y, z, age;
> string name;
>
> let (name, age) = getTuple();           // tuple
> let (x,y,z) = argv[1..4].map!(to!int);  // lazy range
> let (x,y,z) = [1,2,3];                  // array
>
> SomeStruct s;
> let (s.a, s.b) = tuple(3, "piggies");
>
> If a range or array doesn't have enough elements, this thing will throw, and if it's not desired there's
> let (x,y,z)[] = ...
> variant that uses just the available data and keeps the rest variables unchanged.

that's a great example to show d's strength. thank you.

On Thursday, 19 February 2015 at 10:52:40 UTC, Kagamin wrote:
> On Thursday, 19 February 2015 at 09:50:25 UTC, bearophile wrote:
>> I prefer "let", it's much more traditional and descriptive. C++ standard library is often a bad example to follow...
>
> Doesn't "let" normally declare a new variable?

http://ideone.com/iBzuiG - how "let" works in javascript.

Mengu:

> that's a great example to show d's strength. thank you.

It's also a great way to show what's missing in D syntax.

Bye,
bearophile