/// <summary>
/// Returns the smaller of <see cref="Posit8"/> numbers.
/// </summary>
/// <param name="x">The first of two <see cref="Posit8"/> numbers to compare.</param>
/// <param name="y">The second of two <see cref="Posit8"/> numbers to compare.</param>
/// <returns>
/// Parameter <paramref name="x"/> or <paramref name="y"/>,
/// whichever is smaller. If <paramref name="x"/>, <paramref name="y"/>,
/// or both <paramref name="x"/> and <paramref name="y"/>
/// are equal to <c>NaR</c>, that value is returned.
/// </returns>
public static Posit8 Min(Posit8 x, Posit8 y)
{
if (Posit.IsNaR(x) || Posit.IsNaR(y))
{
return(Posit8.NaR);
}
return(x <= y ? x : y);
}
[TestCase(0b00000001, 0b01000001, 0b11000000, "minpos - 1.03125 = -1")] // bitNPlusOne
public void TestSub(byte a, byte b, byte c, string op)
{
var pA = new Posit8(a);
var pB = new Posit8(b);
var pC = new Posit8(c);
Console.WriteLine(op);
Assert.That((pA - pB).ui, Is.EqualTo(pC.ui));
}
/// <summary>
/// Returns the absolute value of a <see cref="Posit8"/> number.
/// </summary>
/// <param name="x">A number that is greater than or equal to MinValue, but less than or equal to MaxValue.</param>
/// <returns>A <see cref="Posit8"/> number, x, such that 0 ≤ x ≤ MaxValue.</returns>
public static Posit8 Abs(Posit8 x)
{
unchecked
{
const int CHAR_BIT = 8;
// http://graphics.stanford.edu/~seander/bithacks.html#IntegerAbs
var mask = (sbyte)x.ui >> sizeof(byte) * CHAR_BIT - 1;
var result = (x.ui ^ mask) - mask;
return(new Posit8((byte)result));
}
}
/// <summary>
/// Returns an integer that indicates the sign of a <see cref="Posit8"/> number.
/// </summary>
/// <param name="x">A signed number.</param>
/// <returns>A number that indicates the sign of <paramref name="x"/></returns>
public static int Sign(Posit8 x)
{
if ((x.ui & ~Posit8.SignMask) == 0)
{
return(0); // Zero or NaR
}
if ((x.ui & Posit8.SignMask) != 0)
{
return(-1); // Negative
}
return(1);
}
public static posit8_t p8_roundToInt(posit8_t a)
{
var(sign, uiA) = a;
if (uiA <= 0x20)
{ // 0 <= |pA| <= 1/2 rounds to zero.
return(Posit8.Zero);
}
else if (uiA < 0x50)
{ // 1/2 < x < 3/2 rounds to 1.
uiA = 0x40;
}
else if (uiA <= 0x64)
{ // 3/2 <= x <= 5/2 rounds to 2.
uiA = 0x60;
}
else if (uiA >= 0x78)
{ // If |A| is 8 or greater, leave it unchanged.
return(a); // This also takes care of the NaR case, 0x80.
}
else
{
var mask = (byte)0x20;
var scale = 0;
while ((mask & uiA) != 0)
{
scale += 1;
mask >>= 1;
}
mask >>= scale;
var bitLast = (uiA & mask) != 0;
mask >>= 1;
byte tmp = (byte)(uiA & mask);
var bitNPlusOne = tmp != 0;
uiA ^= tmp;
tmp = (byte)(uiA & (mask - 1)); //bitsMore
uiA ^= tmp;
if (bitNPlusOne)
{
if (bitLast || (tmp != 0))
{
uiA += (byte)(mask << 1);
}
}
}
return(new Posit8(sign, uiA));
}
public static posit8_t p8_ceil(posit8_t a)
{
var(sign, uiA) = a;
if (uiA == 0)
{
return(a);
}
else if (uiA <= 0x40)
{ // 0 <= |pA| < 1 floor to zero.(if not negative and whole number)
uiA = (byte)((sign && (uiA != 0x40)) ? 0x0 : 0x40);
}
else if (uiA <= 0x60)
{ // 1 <= x < 2 floor to 1 (if not negative and whole number)
uiA = (byte)((sign & (uiA != 0x60)) ? 0x40 : 0x60);
}
else if (uiA <= 0x68)
{ // 2 <= x < 3 floor to 2 (if not negative and whole number)
uiA = (byte)((sign & (uiA != 0x68)) ? 0x60 : 0x68);
}
else if (uiA >= 0x78)
{ // If |A| is 8 or greater, leave it unchanged.
return(a); // This also takes care of the NaR case, 0x80.
}
else
{
byte mask = 0x20, scale = 0;
while ((mask & uiA) != 0)
{
scale += 1;
mask >>= 1;
}
mask >>= scale;
mask >>= 1;
var tmp = (byte)(uiA & mask);
var bitNPlusOne = tmp != 0;
uiA ^= tmp;
tmp = (byte)(uiA & (mask - 1)); //bitsMore
uiA ^= tmp;
if (!sign && (bitNPlusOne || (tmp != 0)))
{
uiA += (byte)(mask << 1);
}
}
return(new Posit8(sign, uiA));
}
/// <summary>
/// Returns <c>e</c> raised to the specified power.
/// </summary>
/// <param name="x">A number specifying a power.</param>
/// <returns>The number <c>e</c> raised to the power <paramref name="x"/>. If <paramref name="x"/> equals NaR, that value is returned.</returns>
public static Posit8 Exp(Posit8 x)
{
return(p8_exp(x));
}
/// <summary>
/// Returns a value with the magnitude of <paramref name="x"/> and the sign of <paramref name="y"/>.
/// </summary>
/// <param name="x">A number whose magnitude is used in the result.</param>
/// <param name="y">A number whose sign is the used in the result.</param>
/// <returns>A value with the magnitude of <paramref name="x"/> and the sign of <paramref name="y"/>.</returns>
public static Posit8 CopySign(Posit8 x, Posit8 y)
{
return(((x.ui ^ y.ui) & Posit8.SignMask) == 0 ? x : -x);
}
/// <summary>
/// Returns the smallest integral value that is greater than
/// or equal to the specified <see cref="Posit8"/> number.
/// </summary>
/// <param name="x">A <see cref="Posit8"/> number.</param>
/// <returns>
/// The smallest integral value that is greater than or equal to
/// <paramref name="x"/>. If <paramref name="x"/> is equal to
/// <c>NaR</c>, that value is returned. Note that this method
/// returns a <see cref="Posit8"/> instead of an integral type.
/// </returns>
public static Posit8 Ceiling(Posit8 x)
{
return(p8_ceil(x));
}
public static posit8_t p8_exp(posit8_t pA)
{
return(new Posit8(p8Exp[pA.ui]));
}
public static bool IsNaR(Posit8 p) => p.ui == Posit8.NaR.ui;
public static bool IsOne(Posit8 p) => p.ui == Posit8.One.ui;
public static bool IsZero(Posit8 p) => p.ui == Posit8.Zero.ui;
public DebugProxy(Posit8 value)
: this(value.ui, Posit8.nbits, Posit8.es)
{
}
public static posit8_t p8_log(posit8_t a)
{
return(a.ui > 127
? Posit8.NaR
: new Posit8(p8Log[a.ui]));
}
/// <summary>
/// Returns the largest integral value less than or equal to the specified <see cref="Posit8"/> number.
/// </summary>
/// <param name="x">A <see cref="Posit8"/> number.</param>
/// <returns>The largest integral value less than or equal to <paramref name="x"/>. If <paramref name="x"/> is equal to <c>NaR</c>, that value is returned.</returns>
public static Posit8 Floor(Posit8 x)
{
return(p8_floor(x));
}
/// <summary>
/// Returns the natural (base e) logarithm of a specified number.
/// </summary>
/// <param name="x">The number whose logarithm is to be found.</param>
/// <returns>The natural logarithm of <paramref name="x"/>; that is, ln x, or log e x. </returns>
/// <remarks>Parameter <paramref name="x"/> is specified as a base 10 number.</remarks>
public static Posit8 Log(Posit8 x)
{
return(p8_log(x));
}
public static bool IsInfinity(Posit8 p) => p.ui == Posit8.Infinity.ui;
/// <summary>
/// Rounds a <see cref="Posit8"/> number to the nearest integral value,
/// and rounds midpoint values to the nearest even number.
/// </summary>
/// <param name="x">A <see cref="Posit8"/> number to be rounded.</param>
/// <returns>
/// The integer nearest <paramref name="x"/>. If the fractional component
/// of <paramref name="x"/> is halfway between two integers, one of which
/// is even and the other odd, then the even number is returned. Note that
/// this method returns a <see cref="Posit8"/> instead of an integral type.
/// </returns>
public static Posit8 Round(Posit8 x)
{
return(p8_roundToInt(x));
}
public static bool IsNegative(Posit8 p) => (sbyte)p.ui < 0;
/// <summary>
/// Returns the square root of a specified number.
/// </summary>
/// <param name="x">The number whose square root is to be found.</param>
/// <returns>One of the values in the following table.
/// <list type="table">
/// <listheader>
/// <term><paramref name="x"/> parameter</term>
/// <term>Return value</term>
/// </listheader>
/// <item>
/// <term>Zero or positive</term>
/// <term>The positive square root of <paramref name="x"/>.</term>
/// </item>
/// <item>
/// <term>Negative</term>
/// <term>NaR</term>
/// </item>
/// <item>
/// <term>NaR</term>
/// <term>NaR</term>
/// </item>
/// </list>
/// </returns>
public static Posit8 Sqrt(Posit8 x)
{
return(p8_sqrt(x));
}
public static bool IsZeroOrNaR(Posit8 p)
{
return((p.ui & (Posit8.SignMask - 1)) == 0);
}
