[jboss-jira] [JBoss JIRA] (DROOLS-1175) Accumulates: sum(Long), sum(BigDecimal), sum(Integer) and sum(BigInteger)

[Geoffrey De Smet (JIRA)]

Geoffrey De Smet created DROOLS-1175:
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             Summary: Accumulates: sum(Long), sum(BigDecimal), sum(Integer) and sum(BigInteger)
                 Key: DROOLS-1175
                 URL: https://issues.jboss.org/browse/DROOLS-1175
             Project: Drools
          Issue Type: Feature Request
          Components: core engine
    Affects Versions: 6.4.0.Final
            Reporter: Geoffrey De Smet
            Assignee: Mario Fusco


Currently, when summing longs in an accumulate, we get something like this:
{code}
when ...
      $t : Number(...) from accumulate(...,
            sum($p.getLongWeight()))
then scoreHolder.addHard($t.longValue());
{code}

This has 3 problems:

- *Loss of precision*: the long sum `1881617265586265321L` will incorrectly return `1.88161726558626534E18`, so `13` too much! The BigDecimal sum of `0.09` and `0.01` will also be incorrect.
- *Loss of performance*: Summing with a Double total is significantly slower than summing with a Long total or an Integer total.
- Example complexity (minor, not all of us agree on this argument): the use of `Number` is an abstraction that doesn't bring any value to the use case. It's worthless complexity.

Solution proposal A) for 7.0 as discussed with Mario:
Based on the argument type to the sum function, the compiler selects a different sum function implementation. This is similar to java overloading mechanism, where `System.out.println(1)` selects a different method implementation than `System.out.println(2.0)`.

Support sum(Long):
{code}
when ...
      $t : Long(...) from accumulate(...,
            sum($p.getLongWeight()))
then scoreHolder.addHard($t);
{code}

and sum(BigDecimal):
{code}
when ...
      $t : BigDecimal(...) from accumulate(...,
            sum($p.getBigDecimalWeight()))
then scoreHolder.addHard($t);
{code}

and also support sum(Integer) and sum(BigInteger).
If this works well, we can consider it for other functions as well in a different jira issue.

Special case 1: sum(Number) should default to sum(Double)
{code}
when ...
      $t : Number(...) from accumulate(...,
            sum($p.getNumberWeight()))
then scoreHolder.addHard($t.doubleValue());
{code}

Not-so-special case 2: the sum integers into a long total, the user should just use:
{code}
      $t : Long(...) from accumulate(...,
            sum((long) $p.getIntWeight()))
{code}



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