1) Groovy does the “right thing” by default

this.a = 0.3
===> 0.3
this.a * 3
===> 0.9
this.a.class.name
===> java.math.BigDecimal

2) Scala behave exactly like Java:

scala> val cent = 0.3
cent: Double = 0.3
scala> cent * 3
res0: Double = 0.8999999999999999

However, using BigDecimal is straightforward thanks to the implicit conversion:

scala> val cent : BigDecimal = 0.3
cent: BigDecimal = 0.3
scala> cent * 3
res1: scala.math.BigDecimal = 0.9

ten_cent = 0.10
sum = 0.0
10.times {sum += ten_cent}
puts “sum is #{sum}”

That results in “1.0” with “native” ruby, and 0.9999 with JRuby.

#include

int main()
{
printf( “%g\n”, 0.3 – 0.2 – 0.1 );
printf( “%g\n”, 0.3 – ( 0.2 + 0.1 ) );
printf( “%g\n”, 0.4 – 0.3 – 0.1 );
printf( “%g\n”, 0.4 – ( 0.3 + 0.1 ) );

return 0;
}