DataMuseum.dk

top - metrics - download

    Length: 2620 (0xa3c)
    Types: TextFile
    Names: »V«

└─⟦180fe333a⟧ Bits:30000405 8mm tape, Rational 1000, SW CATALOG, 10_20_0
└─⟦180fe333a⟧ Bits:30000537 8mm tape, Rational 1000, SW Catalog 10_20_0
    └─⟦5cb1d1d7f⟧ »DATA« 
        └─⟦3b1ee7bd8⟧ 
            └─⟦this⟧ 

TextFile

generic
    type Base is digits <>;
    type Exponent is digits <>;
    type Return_Type is digits <>;
package Raised is
    --==================================================================
    -- This package encapsulates an overloading of the exponential
    -- operator that will raise a floating point number to a floating
    -- point power.
    --
    -- This package attempts to do some minimal numerical analysis in
    -- order to compute the result to the requested accuracy.  The
    -- expression for the termination of the loop comes from the book
    -- "Portability and Style in Ada" by Nissen and Wallis.
    --
    -- The method used to compute the exponentail is based on the
    -- fact that
    --   a ** x = e ** (x * ln(a))
    -- where ln is the natural log function and e is its base.
    -- This is then further refined by saying that x = y.z where
    -- y is the integer part of the number and z is the fractional
    -- part.  Therefore:
    --   a ** x = a ** y.z = a ** (y.0 + 0.z) = (a ** y.0) * (a ** 0.z)
    -- and then calculating a ** y.0 as a ** y using Ada's exponential
    -- function and expanding the other half to be:
    --   (a ** y) * [e ** (0.z * ln(a))]
    -- Now e ** (0.z * ln(a)) is calculated using the Taylor series
    -- expansion:
    --   e ** (0.z * ln(a)) = 1 + 0.z*ln(a) + (0.z*ln(a))**2/2! + ...
    --
    --
    -- Will raise the exception Negative_Base if the user tries to raise
    -- a number <= 0 to a fractional power.
    --
    -- Will raise the exception Value_Too_Large if the result is too
    -- large to compute on the particular machine
    --
    --
    -- Version 2.0 December 6, 1985
    --
    -- Written by Brad Balfour with help and suggestions from
    -- Ed Berard, Johan Margono and Gary Russell
    --==================================================================


    function "**" (Some_Base : in Base; To_The_Power : in Exponent)
                  return Return_Type;
    --===============================================================
    --
    -- calculates a ** x for a and x being floating point numbers.
    --
    -- Version 2.0 December 6, 1985
    --
    -- Written by Brad Balfour with help and suggestions from
    -- Ed Berard, Johan Margono and Gary Russell
    --===============================================================


    Negative_Base : exception;
    --
    -- Raised if the user tries to raise
    -- a number <= 0 to a fractional power.
    --

    Value_Too_Large : exception;
    --
    -- Raised if the result is too
    -- large to compute on the particular machine
    --

end Raised;