Normalize any value in range (-inf…+inf) to (0…1). Is it possible?

Question

If we have concrete range of max..min value it is quite easy to normalize it to 0..1 float values, but if we don\'t have concrete limits? Is it possible to build universal funct

Answer 1

If you don't mind bit-dibbling and are confident that code uses IEEE binary 64-bit floating point, some fast code with only a few FP math operations

// If double is 64-bit  and same endian as integer
double noramlize01(double x) {
  assert(x == x);  // fail if x is NaN
  union {
    double d;
    int64_t i64;
    uint64_t u64;
  } u = {x};
  double d;
  if (u.i64  < 0) {
    u.u64 -= 0x8000000000000000;
    d = (double) -u.i64;
  } else {
    d = (double) u.i64;
  }
  return d/(+2.0 * 0x7ff0000000000000) + 0.5;
}

// Similar test code as this answer

            -inf  0.0000000000000000
  -1.797693e+308  0.0000000000000000
   -3.141593e+00  0.24973844740430023
   -2.718282e+00  0.24979014633262589
   -1.000000e+00  0.25012212994626282
  -2.225074e-308  0.49975574010747437
  -4.940656e-324  0.50000000000000000
   -0.000000e+00  0.50000000000000000
    0.000000e+00  0.50000000000000000
   4.940656e-324  0.50000000000000000
   2.225074e-308  0.50024425989252563
    1.000000e+00  0.74987787005373718
    2.718282e+00  0.75020985366737414
    3.141593e+00  0.75026155259569971
   1.797693e+308  1.0000000000000000
             inf  1.0000000000000000