class
	SIGNAL_MATH

inherit
	SIGNAL_MATH_I

	EROS_REMOTELY_ACCESSIBLE

create
	make

feature -- Basic operations

	cosine_waveform (i_freq, log2_length: INTEGER; phase_fraction: DOUBLE): COLUMN_VECTOR_COMPLEX_64
				-- create a sinusoidal wave
				-- (From Greg Lee's Numeric Eiffel Library test suite)
		local
			c: COMPLEX_DOUBLE
			i_period, i, n: INTEGER
			y, r: DOUBLE
			      do
			n := (2 ^ log2_length).rounded

			i_period := n // i_freq

			y := (2.0 * Pi) / (1.0 * n)

			create Result.make_with_size (n)
			from i := 1 until i > Result.height loop
				r := cosine (i_freq * y * (i - 1 - phase_fraction * i_period))
				c.set(r, 0.0)
				Result.put( c, i )
				i := i + 1
			end
		end

end