This subroutine generates a stored function table by evaluating a polynomial in x over a fixed interval and with specified coefficients.
size -- number of points in the table. Must be a power of 2 or a power-of-2 plus 1.
xval1, xval2 -- left and right values of the x interval over which the polynomial is defined (xval1 < xval2). These will produce the 1st stored value and the (power-of-2 plus l)th stored value respectively in the generated function table.
c0, c1, c2, ... cn -- coefficients of the nth-order polynomial
c0 + c1x + c2x2 + . . . + cnxn
Coefficients may be positive or negative real numbers; a zero denotes a missing term in the polynomial. The coefficient list begins in p7, providing a current upper limit of 144 terms.
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Here is a simple example of the GEN03 routine. It uses the files gen03.orc and gen03.sco. It fills a table with a 4th order polynomial function over the x-interval -1 to 1. The origin will be at the offset position 512. The function is post-normalized. Here is its diagram:
Diagram of the waveform generated by GEN03.
Example 5. A simple example of the GEN03 routine.
/* gen03.orc */ ; Initialize the global variables. sr = 44100 kr = 4410 ksmps = 10 nchnls = 1 ; Instrument #1. instr 1 ; Create an index over the length of our entire note. kcps init 1/p3 kndx phasor kcps ; Read Table #1 with our index. ifn = 1 ixmode = 1 kamp table kndx, ifn, ixmode ; Create a sine wave, use the Table #1 values to control ; the amplitude. a1 oscil kamp*30000, 440, 2 out a1 endin /* gen03.orc */
/* gen03.sco */ ; Table #1: a polynomial function (using GEN03). f 1 0 1025 3 -1 1 5 4 3 2 2 1 ; Table #2, a sine wave. f 2 0 16384 10 1 ; Play Instrument #1 for 2 seconds. i 1 0 2 e /* gen03.sco */