<i18n dev> RFR: 8331485: Odd Results when Parsing Scientific Notation with Large Exponent

[Naoto Sato]

On Fri, 3 May 2024 08:47:03 GMT, Justin Lu <jlu at openjdk.org> wrote:

> Please review this PR which corrects an edge case bug for java.text.DecimalFormat that causes incorrect parsing results for strings with very large exponent values.
> 
> When parsing values with large exponents, if the value of the exponent exceeds `Integer.MAX_VALUE`, the parsed value  is equal to 0. If the value of the exponent exceeds `Long.MAX_VALUE`, the parsed value is equal to the mantissa. Both results are confusing and incorrect.
> 
> For example,
> 
> 
> NumberFormat fmt = NumberFormat.getInstance(Locale.US);
> fmt.parse(".1E2147483648"); // returns 0.0
> fmt.parse(".1E9223372036854775808"); // returns 0.1
> // For comparison
> Double.parseDouble(".1E2147483648"); // returns Infinity
> Double.parseDouble(".1E9223372036854775808"); // returns Infinity
> 
> 
> After this change, both parse calls return `Double.POSITIVE_INFINITY` now.

Looks good. Left some minor comments.

src/java.base/share/classes/java/text/DecimalFormat.java line 2590:

> 2588: 
> 2589:                     if (subparse(text, pos, "", symbols.getMinusSignText(), exponentDigits, true, stat)) {
> 2590:                         // We parse the exponent with isExponent true, thus fitsIntoLong

Nit: `==` or `being` between `isExponent` and `true` may read better.

src/java.base/share/classes/java/text/DecimalFormat.java line 2596:

> 2594:                             exponent = -exponent;
> 2595:                         }
> 2596:                         sawExponent = true;

I see you removed this assignment. I am wondering if we need this variable at all.

test/jdk/java/text/Format/DecimalFormat/LargeExponentsTest.java line 128:

> 126:                 // Trailing zeroes
> 127:                 Arguments.of("1.23E0000123", 1.23E123),
> 128:                 // Trailing zeroes - Past Long.MAX_VALUE length

Leading zeroes?

-------------

PR Review: https://git.openjdk.org/jdk/pull/19075#pullrequestreview-2038744656
PR Review Comment: https://git.openjdk.org/jdk/pull/19075#discussion_r1589560835
PR Review Comment: https://git.openjdk.org/jdk/pull/19075#discussion_r1589558570
PR Review Comment: https://git.openjdk.org/jdk/pull/19075#discussion_r1589573332