[GROOVY-6626] Add a BigInteger.power(Biginteger) method

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.2.2
• Fix Version/s: 2.3.8
• Component/s: groovy-jdk
• Assignee: Pascal Schumacher
• Reporter: Mike Hoolehan
• Created: 18/Mar/14 02:10
• Updated: 17/Dec/14 13:25
• Resolved: 24/Oct/14 16:48

Description

Using the ** operator with a BigInteger as second argument provides in some cases inaccurate results. These results are inconsistent with using a corresponding plain Integer argument.

Examples:

assert 2G ** 63G == 2G ** 63
          |      |     |
          |      false 9223372036854775808
          9223372036854775807

assert 13G ** 15G == 13G ** 15
           |      |      |
           |      false  51185893014090757
           51185893014090760

More examples can be produced with

for (int base = 1; base < 32; base ++) {
    for (int exp = 1; exp < 128; exp++) {
        BigInteger baseI = new BigInteger(base);
        BigInteger expI = new BigInteger(exp);
        if (baseI ** expI != baseI ** exp)
            println "assert ${base}G ** ${exp}G == ${base}G ** ${exp}"
    }
}