feat(stdlib): Number.parseFloat #1288
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ospencer
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phated
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Nov 30, 2022
stdlib/runtime/atof/slow.gr
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| /// Parse the significant digits and biased, binary exponent of a float. | ||
| /// | ||
| /// This is a fallback algorithm that uses a big-integer representation | ||
| /// of the float, and therefore is considerably slower than faster | ||
| /// approximations. However, it will always determine how to round | ||
| /// the significant digits to the nearest machine float, allowing | ||
| /// use to handle near half-way cases. | ||
| /// | ||
| /// Near half-way cases are halfway between two consecutive machine floats. | ||
| /// For example, the float `16777217.0` has a bitwise representation of | ||
| /// `100000000000000000000000 1`. Rounding to a single-precision float, | ||
| /// the trailing `1` is truncated. Using round-nearest, tie-even, any | ||
| /// value above `16777217.0` must be rounded up to `16777218.0`, while | ||
| /// any value before or equal to `16777217.0` must be rounded down | ||
| /// to `16777216.0`. These near-halfway conversions therefore may require | ||
| /// a large number of digits to unambiguously determine how to round. | ||
| /// | ||
| /// The algorithms described here are based on "Processing Long Numbers Quickly", | ||
| /// available here: <https://arxiv.org/pdf/2101.11408.pdf#section.11>. |
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Nit. Drop rust style comments and use a grain block comment
peblair
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Nov 30, 2022
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One minor comment. I admit a lot of the finer details went over my head also (i.e. lemire.gr), but I am reasonably assured that the parsing logic itself and such is correct. It wouldn't hurt to have another team member look it over (cc @marcusroberts and @ospencer), but I'm comfortable approving.
stdlib/runtime/atof/decimal.gr
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| let (==) = WasmI32.eq | ||
| let (+) = WasmI32.add | ||
| let (-) = WasmI32.sub | ||
| // All of the following calls to `trim` are fine because: |
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@jozanza Maybe this comment should refer more precisely to where the call site is (rather than "the following")?
marcusroberts
approved these changes
Dec 3, 2022
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WIP
Trying to implement Lemire with a slow path fallback.
Using these as a reference primarily: