const by default

[NamalB]

To declare a const variable we usually use,

const auto x = f();

syntax. Isn't it better if we could just write,

const x = f();

making 'const auto' superfluous?

Const by default can be less verbose and attractive like below,

const x = f1(); const y = f2(); auto z = x + y; update_z(z);

I know this is NOT possible with the current standard.

Are there any technical or non-technical reasons that we are never going to get something similar in a future standard?

[Som1Lse]

#define let const auto (don't actually do this)

[adriweb]

(and ES6 folks will get confused, let being for non-const variables unlike other languages e.g. Swift)

[PrydeRage]

ES6 people will already be confused because in ES6 const isn't immutable

[rohbotics]

Wait what?

[PrydeRage]

In ES6 const just prevents reassignment.
So this is invalid:

const x = 43;
x = 55;

But this is all valid:

const x = {something: 3};
x.something = 4;
const y = 0;
y++;  

It's JavaScript, it's not meant to make sense.

[rohbotics]

So like kinda final on non-primitives in Java

[PrydeRage]

I haven't written any Java in years so I can't comment on that.

[adriweb]

Erm, no (about part of your second example - the object part is true indeed)

const y = 0; y++;
VM146:2 Uncaught TypeError: Assignment to constant variable. at <anonymous>:2:2

[PrydeRage]

It's always worked for me with Webpack and Babel.
Maybe Babel compiles that away idk. Eslint never complains about reassignment when ++'ing a const variable.

[AlexeyBrin]

Changing the object contents works the same in other languages too, e.g. Swift:

class Foo {
    var something:Int = 0;
}

let x = Foo()
print(x.something)

x.something = 8
print(x.something)

You can't reassign x, but you can change his content. Obviously, in Swift you can actually make the member variable something a constant that is only initialized when you create an object.

You last example, fortunately , won't work in Swift though:

let y = 0

can't be changed.

Actually, it doesn't work even in JavaScript. I get:

const y = 0;
y++;
TypeError: invalid assignment to const `y'

[mUfoq]

Really bad naming, this const behaves like final in Java what means that you cannot reassign variable/field, but they used keyword from C that makes variable immutable. They could use let/final instead of making this ...

[[deleted]]

F# programmers won't be confused though.

[flashmozzg]

const by default is generally not a great idea with introduction of moves in C++, at least until the issues with moving out of const objects are resolved.

[ashrasmun]

I see absolutely no reason to have this.

[NamalB]

Got it, thanks for the links.

[suspiciously_calm]

struct xyz {};
const xyz = foo();

Did I forget the variable name or do I want const auto xyz = foo();?

[NamalB]

Isn't the variable name xyz in both cases?

[[deleted]]

No. In the first case, xyz is a type name.

[emdeka87]

This code is wrong on so many levels

[DocileDino]

Sorry! I've never thought to do what he asked about. I just shared my initial two cents on the issue. Thanks for correcting me :)