dart2js and spec disagree about numerics

[sethladd]

The following Dart code:

var x = 123;
print(x is! double);

will print TRUE in Dart VM and FALSE in JavaScript compiled from Frog.

The generated JavaScript code in question:

print((typeof(x) != 'number'));

doesn't match the intention of the original Dart code.

[DartBot]

This comment was originally written by jat@google.com

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See also issue #638 and lengthy discussions on the mailing list last year.

[dgrove]

Added Area-Frog, Triaged labels.

[gbracha]

I'm generalizing this to tack the numeric discrepancies between the spec (and VM) and the Javascript based implementations.

Consider:

main() {
    int billion = 1000000000;
    int quintillion = billion * billion;
    int quintillionOne = quintillion + 1;
    print(quintillion == quintillionOne);
  }

It compiles without emitting a warning or error, and prints true, which clearly violates the principle of least astonishment.

WE may end up making allowances for JS in some way, but for now this is a bug, and we can track the issue here.

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Changed the title to: "Frog and spec disagree about numerics".

[anders-sandholm]

Removed Area-Frog label.
Added Area-Dart2JS, FromAreaFrog labels.

[kasperl]

Removed FromAreaFrog label.
Changed the title to: "dart2js and spec disagree about numerics".

[DartBot]

This comment was originally written by la...@randompage.org

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We need arbitrary precision integers in our Dart program and have currently implemented our own integer class to get around this bug. Arbitrary precision makes sense for a modern programming language as it's would cause numeric overflows to be a thing of the past.

At any rate please provide some closure on if Dart's integers are arbitrary precision or not.

[sethladd]

The spec says that integers are arbitrary precision. The open issue is how will dart2js accomplish this, with reasonable performance.

[floitschG]

Issue #4478 has been merged into this issue.

[sethladd]

Added this to the M1 milestone.
Removed Priority-Medium label.
Added Priority-High label.

[kasperl]

We do not plan to change the way we deal with ints in dart2js for M1. We will take a look at tackling issue #3814 and issue #4437, but general big int support is not something we're ready to tackle anytime soon.

It remains an issue so I'm certainly keeping the bug open.

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Set owner to @kasperl.
Removed this from the M1 milestone.
Added this to the Later milestone.
Removed Priority-High label.
Added Priority-Medium, Accepted labels.

[kasperl]

cc @larsbak.

[floitschG]

Issue #5827 has been merged into this issue.

[kasperl]

Removed this from the Later milestone.

[kasperl]

Added this to the Later milestone.

[DartBot]

This comment was originally written by ngeoffray@google.com

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Issue #6627 has been merged into this issue.

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cc @karlklose.