Implementation issue for unsigned/triple-shift >>> operator

[floitschG]

This is the implementation issue for the triple-shift >>> operator (unsigned shift), see language feature #120

The operator has the same precedence as >>.
The expression e1 >>> e2 is a compile-time constant expression if both e1 and e2 are compile-time constant expressions evaluating to integers (and int will implement the operator).
The symbol #>>> is valid (along with const Symbol(">>>")), as is x >>>= e as an expression.

Adding the new operator is non-breaking.

• specification
• Frontend Handle the unsigned shift operator in the frontend sdk#30888
• Analyzer Handle the unsigned shift, triple-shift, >>> operator in analyzer sdk#44908
• dart2js Handle the unsigned shift operator in dart2js sdk#30890
• DDC Handle the unsigned shift operator in DDC sdk#30891
• VM Implement the triple shift operator sdk#30892

[rashedmyt]

waiting for this operator to be in release

[kevmoo]

@lrhn what's the story with this?

@aadilmaan @mit-mit – are we tracking this somewhere?

Related: https://stackoverflow.com/questions/57190508/does-dart-have-operator/57210971

[mit-mit]

This is now tracked in #120. Closing the present historical issue.

[mit-mit]

Transferring and re-purposing to be the implementation issue for this feature. Please note that this isn't currently being implemented, it's just ready for implementation.

[AKushWarrior]

Is there a status on this? It would be massively helpful for cryptography.

[AKushWarrior]

I don't think this would be too difficult. I haven't tried forking dart's internals, but I'm using a utility extension function. Converted to an operator, it would look like. (EDIT: JS is hard)

int operator >>> (int n) {
    return ((this >= 0) ? this >> (n) : ~(~this >> (n)));
}

[AKushWarrior]

The code snippet I posted was wrong. I fixed it.

It's tested and works on the VM, but does not work when trans-piled to JS.

[AKushWarrior]

New code snippet, which works both on the VM and when trans-piled to JS. (EDIT: it doesn't; it's broken for JS for negative numbers; see below)

  int operator >>> (int count) {
    if (!isJS) {
      return (this >= 0) ? this >> count : ~(~this >> count);
    } else {
      count &= 0x1f;
      if (this >= 0) {
        return (this >> count + 1);
      } else {
        var mask = 1 << (31 - count);
        return (~this >> count) | mask;
      }
    }
  }

  bool get isJS {
    // Some definition here...
  }

I dunno about performance, but I use only bitwise operators, so it should be decent. It's tested on the VM and DartPad. All cases (negative, zero, positive) check out for both.

If someone could guide me through the process, I'd be happy to try and implement the >>> operator as a language feature.

[mpfaff]

@AKushWarrior what is x supposed to be in your code example?