JDK-8295391: Add discussion of binary <-> decimal conversion issues #16566

jddarcy · 2023-11-08T17:29:28Z

Add discussion of some of the common pitfalls related to decimal <-> binary conversion.

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Issue

JDK-8295391: Add discussion of binary <-> decimal conversion issues (Enhancement - P4)

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Brian Burkhalter (@bplb - Reviewer) ⚠️ Review applies to 0ac7125c

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bridgekeeper · 2023-11-08T17:30:29Z

👋 Welcome back darcy! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2023-11-08T17:33:17Z

@jddarcy The following label will be automatically applied to this pull request:

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mlbridge · 2023-11-08T17:39:10Z

Webrevs

src/java.base/share/classes/java/lang/Double.java

rgiulietti · 2023-11-08T19:01:20Z

What about adding a link to this discussion in the doc for j.l.Float? After all, the discussion contains many float examples.

bplb

Looks fine.

openjdk · 2023-11-08T19:10:29Z

@jddarcy This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8295391: Add discussion of binary <-> decimal conversion issues

Reviewed-by: bpb

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

99570fb: 8320258: Refresh building.md

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eirbjo

Left some minor proofreading comments. (Not a Reviewer)

eirbjo · 2023-11-08T18:41:53Z

src/java.base/share/classes/java/lang/Double.java

+ * Many surprising aspects of binary floating-point arithmetic trace
+ * back to aspects of decimal to binary conversion and binary to
+ * decimal conversion. While integer values can be exactly represented
+ * in any base, which fractional values can be exactly represented is
+ * a function of the base. For example, in base 10, 1/3 is a repeating


Could the first sentence be simplified and "de-aspectized"? Suggestion: "..trace back to conversions between binary and decimal representations".

The second sentence has a suspicious while/which pairing and "represented is" should probably be "represented as". Suggestion: "While integer values can be exactly represented in any base, fractional values can only be exactly represented as a function of the base."

Thanks for the close reading; I made another few passes over the text based on your comments.

eirbjo · 2023-11-08T18:46:53Z

src/java.base/share/classes/java/lang/Double.java

+ * double}. Alternatives include using an integer type and storing
+ * cents or mills or using {@link java.math.BigDecimal BigDecimal} to
+ * store decimal fraction values exactly.


The "and,or,or" sequence makes this sentence somewhat hard to parse. Perhaps a bit of punctuation could help readability?

eirbjo · 2023-11-08T18:50:14Z

src/java.base/share/classes/java/lang/Double.java

+ * store decimal fraction values exactly.
+ *
+ * <p>For each finite floating-point value and a given floating-point
+ * type, there is a contiguous region of the real number line which


Neither English nor floating-point are native to me, but would it be better to use "region on the real number line" here?
A quick Google search of the alternatives gives 4 results for "region of.." and 22.000 for "region on.."

eirbjo · 2023-11-08T19:03:09Z

src/java.base/share/classes/java/lang/Double.java

+ * <li>equal to the exact result
+ * </ul>
+ *
+ * A floating-point value doesn't "know" if it was the result of


Would it be better to use "whether" in this listing of alternatives? (As recommended by Merriam-Webster: https://www.merriam-webster.com/grammar/if-vs-whether-difference-usage)

eirbjo · 2023-11-08T19:10:08Z

src/java.base/share/classes/java/lang/Double.java

+ * }
+ *
+ * should <em>not</em> be expected to be exactly equal to 1.0, but
+ * only close to 1.0. Consequently the following code is an infinite loop:


I think "Consequently" is a conjunctive adverb here, so should be followed by a comma. Or perhaps just drop it, since the previous sentence also starts with "Consequently, "

eirbjo · 2023-11-08T19:15:59Z

src/java.base/share/classes/java/lang/Double.java

+ * Float.valueOf("0.100000005215406417846679687499999");  // rounds down to oneTenthApproxAsFloat
+ * }
+ *
+ * <p>An analogous range can be constructed similarly for the {@code


Suggested change

* <p>An analogous range can be constructed similarly for the {@code

* <p>Similarly, an analogous range can be constructed for the {@code

eirbjo · 2023-11-08T19:20:44Z

src/java.base/share/classes/java/lang/Double.java

+ * }
+ * }
+ *
+ * Instead, for counted loops, use an integer loop count:


Suggested change

* Instead, for counted loops, use an integer loop count:

* Instead, use integer loop counters for counted loops:

bplb · 2023-11-08T19:40:11Z

src/java.base/share/classes/java/lang/Double.java

@@ -749,7 +882,7 @@ public static String toHexString(double d) {
     * @return     a {@code Double} object holding the value
     *             represented by the {@code String} argument.
     * @throws     NumberFormatException  if the string does not contain a
-     *             parsable number.


Was parsable number supposed to be deleted?

My mistake in editing; I'll correct it. Thanks.

jddarcy · 2023-11-18T01:18:14Z

/integrate

openjdk · 2023-11-18T01:19:26Z

Going to push as commit 8ff7d6e.
Since your change was applied there has been 1 commit pushed to the master branch:

99570fb: 8320258: Refresh building.md

Your commit was automatically rebased without conflicts.

openjdk · 2023-11-18T01:19:34Z

@jddarcy Pushed as commit 8ff7d6e.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

JDK-8295391: Add discussion of binary <-> decimal conversion issues

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Address issues found by reviewers.

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Switch to parseFloat from valueOf, add links.

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jddarcy added 8 commits November 8, 2023 11:49

Fix typo.

d8d6c00

Merge branch 'master' into JDK-8295391

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Merge branch 'master' into JDK-8295391

eaca9e2

Grammar updates.

b7aa06a

Minor rewordings.

d18ff5c

Small clean ups.

3730f39

Minor tweaks.

b7a18ad

Fix link.

58e5189

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JDK-8295391: Add discussion of binary <-> decimal conversion issues #16566

JDK-8295391: Add discussion of binary <-> decimal conversion issues #16566

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	* <p>An analogous range can be constructed similarly for the {@code
	* <p>Similarly, an analogous range can be constructed for the {@code

	* Instead, for counted loops, use an integer loop count:
	* Instead, use integer loop counters for counted loops:

JDK-8295391: Add discussion of binary <-> decimal conversion issues #16566

JDK-8295391: Add discussion of binary <-> decimal conversion issues #16566

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jddarcy commented Nov 8, 2023 • edited by openjdk bot Loading

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