Strange float behaviour on Arduino Mega

[gfvalvo]

@bojan_jurca

It seems that floats can contain the exact number 0.090650305151939.

Nope.

@kenb4

No; for any exact binary floating point value with digits to the right of the decimal point, the last non-zero digit must be a 5: 0.5, 0.25, 0.125, 0.0625 etc.

Put another way, consider a proper, irreducible fraction of the form N/D. The value is exactly representable in binary (meaning with a finite number of bits to the right of the binary point) if an only if D = 2^p, where p = 1, 2, 3, 4, 5, ….