internal override void Propagate(ref bool fail)
{
if (NarrowedVariable != this.power)
{
this.power.NarrowTo(this.a.Value ^ this.exponent, ref fail);
if (fail)
{
return;
}
}
// We want to repropagate in case this is an even power and we just split on a.
//if (NarrowedVariable != this.a)
{
if ((exponent % 2 == 0) && this.a.Value.Lower < 0)
{
if (this.a.Value.Upper <= 0)
{
// a is non-positive
this.a.NarrowTo(-Interval.InvPower(power.Value, exponent), ref fail);
}
else
{
// even inverse power of an interval that crosses zero
var bound = Interval.InvPower(power.Value, exponent).Upper;
this.a.NarrowTo(new Interval(-bound, bound)
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, ref fail);
}
}
else
{
// a is already non-negative or exponent is odd (and so function is monotone)
this.a.NarrowTo(Interval.InvPower(this.power.Value, this.exponent), ref fail);
}
}
}