Comments (19)
DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
This is standard IEE 754 behavior: 1/0 = +Infinity, -1/0 = -Infinity, Infinity/Infinity = NaN. Dart isn't doing anything differently here than either Java or JavaScript.
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
(IEE ==> IEEE)
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
You mean just Javascript.
Even though the following does produce Infinity and NaN:
<html>
<body>
<script>
alert(1/0);
alert((1/0)/(1/0));
</script>
</body>
</html>
It is invalid in Java, e.g.:
public class Test {
public static void main(String args[]) {
System.out.println( "" + (1/0));
System.out.println( "" + ((1/0)/(1/0)));
}
}
results in:
$ java Test
Exception in thread "main" java.lang.ArithmeticException: / by zero
at Test.main(Test.java:3)
Still, Dart is a new language. Couldn't it aspire to get math right instead of being just another Javascript?
Thanks!
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
Your Java example is dividing ints, not (IEEE 754) floats or doubles. Please replace 1 with 1.0 and 0 with 0.0 and give your code another try.
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
IEEE 754 is what hardware implements -- so adopting a different set of semantics for floating-point numbers means relying on software to do the heavy lifting, and puts code at a big disadvantage versus code that is designed to take advantage of what the floating-point hardware can do.
I thing there is a separate issue of how dividing ints should behave in Dart -- note that the / operator produces a num, not an int, even when dividing two ints. For example, 1/2 = 0.5, like JavaScript, not 0 as in Java. There is a ~/ operator that truncates to int. Currently, (1 ~/ 0) also evaluates to Infinity -- this seems like it would be worth taking up with the spec folks.
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
Yes, for Float and Double, but fails again with BigDecimal:
import java.math.BigDecimal;
public class Test {
public static void main(String args[]) {
System.out.println( "" + (1F/0F));
System.out.println( "" + ((1F/0F)/(1F/0F)));
System.out.println( "" + (1D/0D));
System.out.println( "" + ((1D/0D)/(1D/0D)));
System.out.println( "" + (new BigDecimal(1D).divide(new BigDecimal(0D), BigDecimal.ROUND_UNNECESSARY)));
System.out.println( "" + ((new BigDecimal(1D).divide(new BigDecimal(0D), BigDecimal.ROUND_UNNECESSARY)).divide(new BigDecimal(1D).divide(new BigDecimal(0D), BigDecimal.ROUND_UNNECESSARY), BigDecimal.ROUND_UNNECESSARY)));
}
}
Produces:
$ java Test
Infinity
NaN
Infinity
NaN
Exception in thread "main" java.lang.ArithmeticException: / by zero
at java.math.BigDecimal.divide(BigDecimal.java:1327)
at java.math.BigDecimal.divide(BigDecimal.java:1444)
at Test.main(Test.java:9)
But it looks like Ruby 1.8.7 still does what you are saying even with BigDecimal:
$ irb
1/0
ZeroDivisionError: divided by 0
from (irb):1:in `/'
from (irb):1
1.0/0.0
=> Infinity
(1.0/0.0)/(1.0/0.0)
=> NaN
require 'bigdecimal'
BigDecimal("1.0") / BigDecimal("0.0")
=> #<BigDecimal:100605f80,'Infinity',4(24)>
(BigDecimal("1.0") / BigDecimal("0.0")) / (BigDecimal("1.0") / BigDecimal("0.0"))
=> #<BigDecimal:1005fbff8,'NaN',4(56)>
Oh, well. It's a shame that we still settle for that. :)
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
You can close this if you want. Sorry to bother about it.
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
Oops, just saw your other comment. Yes, feel free to take up with the spec folks about ints being treated as floating points. Glad I could be of limited assistance.
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floitschG
commented on August 25, 2024
DartC (the compiler from Dart to JavaScript) is not spec-compliant with regards to numbers. We compile dart numbers to JavaScript numbers (thus losing the distinction between ints and doubles).
dart: x / 0 throws a DivisionByZeroException in correct Dart. In dart->Js code it unfortunately becomes the equivalent of x / 0.0 which becomes infinity/nan.
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
Added Area-Language, Triaged labels.
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gbracha
commented on August 25, 2024
The spec was carefully thought out and it describes the intended semantics of Dart. We make allowances for dartC, and maybe it is unreasonable to do the right thing and still be performant. But AFIK, this isn't a spec issue unless we want to enshrine special dispensation for dartC in the spec.
Removed Area-Language label.
Added Area-Compiler label.
Changed the title to: "dartC compiles both ints and doubles into Javascript numbers".
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
To me, it seems that JS is correct here. 1/0 is infinity. infinity / infinity is undefined, a.k.a. NaN.
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
As Florian said, the original target for the java-based dartc was to compile dart numbers to JS numbers.
The only thing that we can do here is to decide whether it is worth checking for division by zero in the current dartc or not -- I changed the description accordingly.
Changed the title to: "dartc does not generate DivisionByZeroException errors".
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DartBot
commented on August 25, 2024
This comment was originally written by [email protected]
Unassigned from area=compiler. This bug is no longer valid for dartc, but I believe is still a general dart to Javsscript translation issue. If not, please close.
Removed Area-Compiler label.
Added New label.
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anders-sandholm
commented on August 25, 2024
Added Area-Dart2JS, Triaged labels.
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kasperl
commented on August 25, 2024
Changed the title to: "Make sure dart2js generates DivisionByZeroException errors".
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kasperl
commented on August 25, 2024
Update summary to reflect that we haven't decided yet.
Changed the title to: "Decide if we want to generate DivisionByZeroException errors".
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kasperl
commented on August 25, 2024
Added this to the Later milestone.
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kasperl
commented on August 25, 2024
Removed this from the Later milestone.
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