[OASIS Issue Tracker] (ODATA-784) Need to specify the behaviour of arithmetic operators on Decimal type

[OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>]

    [ https://issues.oasis-open.org/browse/ODATA-784?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=61040#comment-61040 ] 

Evan Ireland commented on ODATA-784:
------------------------------------

The Java preferred division scale is only for *exact* division with divide(BigDecimal divisor) 
  Returns a BigDecimal whose value is (this / divisor), and whose preferred scale is (this.scale() - divisor.scale()); if the exact quotient cannot be represented (because it has a non-terminating decimal expansion) an ArithmeticException is thrown.

The BigDecimal methods that accept a rounding mode use the rule: scale(A div B) = scale(A)

(which is greater than scale(A) - scale(B))

Consider also the following:

X / 2.0

is equivalent to

X * 0.5

for which we would apply the rule scaleof(A mul B) = scaleof(A) + scaleof(B).

So sticking with scaleof(A mul B) = scaleof(A) + scaleof(B) seems the most reasonable.

> Need to specify the behaviour of arithmetic operators on Decimal type
> ---------------------------------------------------------------------
>
>                 Key: ODATA-784
>                 URL: https://issues.oasis-open.org/browse/ODATA-784
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Improvement
>          Components: OData URL Conventions
>    Affects Versions: V4.0_OS
>         Environment: Proposed
>            Reporter: Evan Ireland
>            Priority: Minor
>             Fix For: V4.01_WD01, V4.0_ERRATA03
>
>
> The rules for scale of results of decimal arithmetic operators are not specified.



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