Issue #12780 has been updated by Shyouhei Urabe.


We (mainly mrkn and matz) discussed why Fixnum#round returns Integer today.  The answer is because (unlike other languages, namely C's round(3)) in ruby we can safely store all possible return value that round can theoretically generate, in Integer.

BigDecimal#round's returning BigDecimal instance sounds nice.  But matz said he need to think a while for this historic Float behaviour.

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Bug #12780: BigDecimal#round returns different types depending on argument
https://bugs.ruby-lang.org/issues/12780#change-61728

* Author: Dawid Janczak
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* ruby -v: ruby 2.4.0dev (2016-09-21 trunk 56199) [x86_64-linux]
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
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BigDecimal#round returns Integer when no arguments are given and BigDecimal otherwise. I would have assumed the result to always be BigDecimal.

BigDecimal.new('12.34').round # => 12 (Integer)
BigDecimal.new('12.34').round(0) # => 12 (BigDecimal)

Attached is a patch with possible fix.

I found a similar issue to this one (https://bugs.ruby-lang.org/issues/2662), but it's in Japanese. If this should be rejected as well could someone provide an explanation in English please? Also in that case documentation should be changed as it clearly states that the result should be BigDecimal: "Round to the nearest integer (by default), returning the result as a BigDecimal."

---Files--------------------------------
bigdecimal_round.diff (969 Bytes)


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