Stupid float implementation from uint8

f2x8.py

import numpy as np

def to_float32(exponent, significand):
    assert exponent.dtype == np.uint8
    assert significand.dtype == np.uint8
    negative = ((exponent & 128) >> 7) == 1
    exponent = (exponent & 127).astype(float)-64
    value = 2.0**exponent * (1.0 + significand.astype(float) / 256.0)
    value[negative] *= -1
    return value

def from_float32(value):
    sign = (128 * (value < 0)).astype(np.uint8)
    value = abs(value)
    exponent = np.floor(np.log2(value))
    if (exponent >= 64).any() or (exponent <= -65).any():
        raise ValueError('doesnt fit in exponent')
    significand = (value / 2**exponent - 1) * 256
    exponent = ((exponent+64).astype(np.uint8)) | sign
    significand = significand.astype(np.uint8)
    return exponent, significand

es = np.arange(256*256, dtype=np.uint16)
e, s = (es >> 8).astype(np.uint8), (es & 255).astype(np.uint8)

v = to_float32(e, s)
e2, s2 = from_float32(v)
v2 = to_float32(e2, s2)


print('exp    ok?', (e2 == e).mean())
print('sig    ok?', (s2 == s).mean())
print('v      ok?', (v2 == v).mean())
print('order+ ok?', (np.diff(v[v>0]) > 0).mean())
print('order- ok?', (np.diff(v[v<0]) < 0).mean())