func next_term(k int64) {
y2 := k*2 + 1
tmp1 = numer.Shl(1)
bignum.Iadd(accum, accum, tmp1)
bignum.Iscale(accum, y2)
bignum.Iscale(numer, k)
bignum.Iscale(denom, y2)
}
func extract_digit() int64 {
if numer.Cmp(accum) > 0 {
return -1
}
// Compute (numer * 3 + accum) / denom
tmp1 = numer.Shl(1)
bignum.Iadd(tmp1, tmp1, numer)
bignum.Iadd(tmp1, tmp1, accum)
tmp1, tmp2 := tmp1.QuoRem(denom)
// Now, if (numer * 4 + accum) % denom...
bignum.Iadd(tmp2, tmp2, numer)
// ... is normalized, then the two divisions have the same result.
if tmp2.Cmp(denom) >= 0 {
return -1
}
return tmp1.Value()
}