Number.prototype.toHexExponential
This is similar to 'toExponential' but is in the normalised hexadecimal
form instead of decimal.
E.g. 1.4A2p+4
The letter 'p' corresponds to decimal's 'e', and means "times 2 to the
power of".
The *binary* exponent is represented in signed *decimal*.
The hex representation should probably be in lowercase to match that of
'toString(16)'.
GNU's printf provides this format with its %a and %A conversions. The
format is useful for transferring arbitrary binary floating-point values
exactly, whereas decimal formats round them.
Number.prototype.toString() generates as many digits as needed for the
number to be representable unambiguously.
(if I wanted packed binary number representation, then rather some form of
base32 - it packs more)
True about the decimal representation - the case for unambiguous transfer is
weak.
The objective of hexadecimal exponential representation is not to achieve
dense packing; rather to represent a binary64 value in a common
programmer-friendly (i.e. hexadecimal) form. Note the natural match with
the binary64 sign-significand-exponent fields.
Some Prior Art:
1) GNU's printf does this with %a and %A conversions, (other printf
versions too?).
2) C (after C99) has hexadecimal exponential literals (see my new post
"hexadecimal literals for floating-point").
3) (I believe) IEEE 754-2008 specifies it.
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