public static EInteger IntegerDigitLengthUpperBound <THelper>(
IRadixMathHelper <THelper> helper,
THelper val)
{
// Gets an upper bound on the number of digits in the integer
// part of the given number 'val'.
int flags = helper.GetFlags(val);
if ((flags & BigNumberFlags.FlagSpecial) != 0)
{
// Infinity and NaN are not supported
throw new NotSupportedException();
}
EInteger expo = helper.GetExponent(val);
EInteger mant = helper.GetMantissa(val).Abs();
if (expo.Sign <= 0)
{
// Exponent Y in X*digits^Y is 0 or negative, so upper bound
// of significand's digit count works by itself.
return(DigitLengthUpperBound(helper, mant).ToEInteger());
}
else
{
return(DigitLengthUpperBound(helper, mant).ToEInteger().Add(expo));
}
}
public static THelper PreRound <THelper>(
THelper val,
EContext ctx,
IRadixMath <THelper> wrapper)
{
if (ctx == null || !ctx.HasMaxPrecision)
{
return(val);
}
IRadixMathHelper <THelper> helper = wrapper.GetHelper();
int thisFlags = helper.GetFlags(val);
if ((thisFlags & BigNumberFlags.FlagSpecial) != 0)
{
// Infinity or NaN
return(val);
}
FastInteger fastPrecision = FastInteger.FromBig(ctx.Precision);
EInteger mant = helper.GetMantissa(val).Abs();
// Rounding is only to be done if the digit count is
// too big (distinguishing this case is material
// if the value also has an exponent that's out of range)
FastInteger[] digitBounds = NumberUtility.DigitLengthBounds(
helper,
mant);
if (digitBounds[1].CompareTo(fastPrecision) <= 0)
{
// Upper bound is less than or equal to precision
return(val);
}
EContext ctx2 = ctx;
if (digitBounds[0].CompareTo(fastPrecision) <= 0)
{
// Lower bound is less than or equal to precision, so
// calculate digit length more precisely
FastInteger digits = helper.GetDigitLength(mant);
ctx2 = ctx.WithBlankFlags().WithTraps(0);
if (digits.CompareTo(fastPrecision) <= 0)
{
return(val);
}
}
val = wrapper.RoundToPrecision(val, ctx2);
// the only time rounding can signal an invalid
// operation is if an operand is a signaling NaN, but
// this was already checked beforehand
#if DEBUG
if ((ctx2.Flags & EContext.FlagInvalid) != 0)
{
throw new ArgumentException("doesn't" +
"\u0020satisfy(ctx2.Flags&FlagInvalid)==0");
}
#endif
if ((ctx2.Flags & EContext.FlagInexact) != 0)
{
if (ctx.HasFlags)
{
ctx.Flags |= BigNumberFlags.LostDigitsFlags;
}
}
if ((ctx2.Flags & EContext.FlagRounded) != 0)
{
if (ctx.HasFlags)
{
ctx.Flags |= EContext.FlagRounded;
}
}
if ((ctx2.Flags & EContext.FlagOverflow) != 0)
{
bool neg = (thisFlags & BigNumberFlags.FlagNegative) != 0;
if (ctx.HasFlags)
{
ctx.Flags |= EContext.FlagLostDigits;
ctx.Flags |= EContext.FlagOverflow |
EContext.FlagInexact | EContext.FlagRounded;
}
}
return(val);
}