Numeric#round(n, mode) - round modes are not supported

[deepj]

At least Ruby 2.4 supports several round modes. See https://ruby-doc.org/stdlib-2.4.0/libdoc/bigdecimal/rdoc/BigDecimal.html#method-c-mode

Unfortunately, TruffleRuby triggers TypeError: Truffle doesn't have a case for the org.truffleruby.stdlib.bigdecimal.BigDecimalNodesFactory$RoundNodeFactory$RoundNodeGen node with values of type exception with any used round mode.

To reproduce:

require 'bigdecimal'

BigDecimal('1.516').round(2, :half_even)

Error:

TypeError: Truffle doesn't have a case for the org.truffleruby.stdlib.bigdecimal.BigDecimalNodesFactory$RoundNodeFactory$RoundNodeGen node with values of type  Truffle::BigDecimal(com.oracle.truffle.object.basic.DynamicObjectBasic) java.lang.Integer=2 Symbol(com.oracle.truffle.object.basic.DynamicObjectBasic)
	from (irb):5:in `round'
	from (irb):5
	from ~/.rubies/truffleruby-1.0.0-rc10/bin/irb:29:in `<main>'

[nirvdrum]

Thanks for the report. TruffleRuby does work with some round modes. It passes all the BigDecimal#round specs. It looks like the symbol-based modes are problematic. We probably need a lookup table to translate them to integer values. It shouldn't be too difficult.

It looks like we should also improve the Ruby Spec Suite by adding more cases to test.

[nirvdrum]

Are you sure that's supposed to work though? In MRI 2.4.x and 2.5.x, I get an ArgumentError:

> BigDecimal('1.516').round(2, :round_half_even)
ArgumentError: invalid rounding mode
	from (irb):2:in `round'
	from (irb):2
	from /home/kjmenard/.rbenv/versions/2.4.4/bin/irb:11:in `<main>'

So it looks like we might just need raise an ArgumentError with a better message.

[deepj]

@nirvdrum You have a typo. It's half_even, not round_half_even :)

[deepj]

[nirvdrum]

Right you are. I messed up translating BigDecimal::ROUND_HALF_EVEN to a symbol. Thanks for pointing that out.

[chrisseaton]

The three rounding issues #1509, #1510, #1514.

[deepj]

@eregon @chrisseaton Could this be a priority for RC14, please? In fact, this is one of issues why I started to report bugs in TruffleRuby. I'd like to run a quite trivial script importing exchange rates on TruffleRuby one day :)

[chrisseaton]

Sorry this hasn't managed to go into RC15, but we have a lot of time scheduled this month to look at this issue backlog.

[chrisseaton]

Working on this now.

[chrisseaton]

Fix for this done and on the way.

[chrisseaton]

Fixed in 0beec8a.