haskell / haskell/math-functions

invIncompleteBeta fails for some (exotic) inputs

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bug
Dominant language
Haskell
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Description

```
*Numeric.SpecFunctions.Internal> invIncompleteBeta 9 2 1e-300
*** Exception: Numeric.SpecFunctions.incompletBeta_: x out of [0,1] range. p=9.0 q=2.0 x=NaN
```

It fails in Halley step when derivative of incomplete beta underflows and becomes zero so no next approximation could be computed, It happens for large `a` and small `x`.

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