[... -0 in string conversion ...]
(-0).toFixed(0) -> "0"
Is this a bug in the spec for toFixed?
I would say it's deeper than that. It's about JavaScript's philosophy
towards -0. Particularly as expressed in the ToString internal function
(*). If ToString is fixed then single-element Array conversion and JSON
stringification work right.
(*) I.e. steps 2 & 3 of ToString as shown in section 9.8.1 "ToString Applied
to the Number Type".
If we accept the need for -0 -- and the precise & correct care taken in Math
and arithmetic shows that we do -- then why go off the rails when it comes
to string conversion?
In the specific case of Number.prototype.toFixed you could change step 6 to
"If x is negative, then", providing the term "negative" is suitably defined.
The same goes for Number.prototype.toExponential etc etc.
Note the broken symmetry:
ToString is surjective but not injective; ToNumber is both surjective and
injective.
ToString and ToNumber are not inverses:
ToNumber("-0") -> -0
but
ToString(-0) -> "0"
Of course, in the language (-0 < 0) is false. See 5.2 Algorithm
Conventions.
It is mathematically proper than (-0 < 0) is false. Only if one imposes a
Total Order over the set of Number does that expression become true.
(IEEE754 has a cmpTotalOrder function which does this, and includes normal
and signaling NaNs, and can include NaN payloads if anybody cares).
Am I missing something: Does section 5.2 actually say anything worthwhile at
all?
Flippantly, it seems to be no more than:
"Abstract mathematical arithmetic and functions have exact values, but a
finite machine can only deal with floating-point approximations. This
standard does limited-precision floating-point not impossible
infinite-precision because we cannot wait an eternity for the result and
there is not enough energy or matter in the Universe to compute or store an
infinitely precise result. Intermediate results will be rounded. Buy a
textbook on Numerical Analysis, or take your chances."
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