/*
Y_x4p_i - Calcucaltes a Y value from a given X and 2 pairs of X/Y points, at init-time
DESCRIPTION
Performs a simple linear equation at init-time. The x-range is given by two points x1 and x2; the y-range by y1 and y2. The function returns the y value for a given x.
See the example below for a practical application (instr 1).
SYNTAX
iy Y_x4p_i ix, ix1, ix2, iy1, iy2
INITIALIZATION
ix1, iy1 - two points related to each other
ix2, iy2 - two other points related to each other
ix - another x value
iy - y value related to ix
CREDITS
joachim heintz 2011
*/
opcode Y_x4p_i, i, iiiii
ix, ix1, ix2, iy1, iy2 xin
imm = (iy2-iy1) / (ix2-ix1)
inn = iy1 - imm*ix1
iy = imm*ix + inn
xout iy
endop