# compute arctangent table for CORDIC computations in fttrigon.c

import sys, math

#units  = 64*65536.0   # don't change !!

units  = 256

scale  = units/math.pi

shrink = 1.0

comma  = ""

def calc_val( x ):

    global units, shrink

    angle  = math.atan(x)

    shrink = shrink * math.cos(angle)

    return angle/math.pi * units

def  print_val( n, x ):

    global comma

    lo  = int(x)

    hi  = lo + 1

    alo = math.atan(lo)

    ahi = math.atan(hi)

    ax  = math.atan(2.0**n)

    errlo = abs( alo - ax )

    errhi = abs( ahi - ax )

    if ( errlo < errhi ):

      hi = lo

    sys.stdout.write( comma + repr( int(hi) ) )

    comma = ", "

print ""

print "table of arctan( 1/2^n ) for PI = " + repr(units/65536.0) + " units"

# compute range of "i"

r = [-1]

r = r + range(32)

for n in r:

    if n >= 0:

        x = 1.0/(2.0**n)    # tangent value

    else:

        x = 2.0**(-n)

    angle  = math.atan(x)    # arctangent

    angle2 = angle*scale     # arctangent in FT_Angle units

    # determine which integer value for angle gives the best tangent

    lo  = int(angle2)

    hi  = lo + 1

    tlo = math.tan(lo/scale)

    thi = math.tan(hi/scale)

    errlo = abs( tlo - x )

    errhi = abs( thi - x )

    angle2 = hi

    if errlo < errhi:

        angle2 = lo

    if angle2 <= 0:

        break

    sys.stdout.write( comma + repr( int(angle2) ) )

    comma = ", "

    shrink = shrink * math.cos( angle2/scale)

print

print "shrink factor    = " + repr( shrink )

print "shrink factor 2  = " + repr( shrink * (2.0**32) )

print "expansion factor = " + repr(1/shrink)

print ""