Add Choose[BigInt]

[dmurvihill]

ScalaCheck's arbitrary BigInt is bounded, which can be very limiting for some applications and requires e.g. scientific and cryptographic users to implement custom generators. Providing a Choose[BigInt] implementation could save considerable boilerplate. This is my implementation:

  implicit object chooseBigInt extends Gen.Choose[BigInt] {
    @tailrec
    def choose(min: BigInt, max: BigInt): Gen[BigInt] = {
      val n = min + BigInt((max - min).bitLength, Random)
      if (n > max) choose(min, max) else n
    }
  }

Any interest in a PR?

[ashawley]

Yeah, the bounds of arbitrary BigInt is by design. An implementation of Gen.choose[BigInt](min,max) is missing, however. Yes, a contribution would be welcome for BigInt, and for BigDecimal if you're interested.

[ashawley]

A ticket for BigDecimal is #637. I thought there might be some commonality, but it seems like BigInt may be a dependency of BigDecimal.

[ashawley]

@dmurvihill has an open PR in #636. We began to realize that there are practical limits of what ScalaCheck can offer in coverage of BigInt values in terms of performance. As @non pointed out, there are other practical issues, including printing large failing BigInt values. Given these limits, I wonder what safe guards ScalaCheck should provide to Gen.choose[BigInt]?