Float32 -> string --> Float32 round trip not possible for strconv.FormatFloat 'b' ?

[Glen Newton]

Hello,

I am using strconv.FormatFloat[1] and strconv.ParseFloat[2]to convert float32s back-and-forth in a library I am working on. In my tests I decided to test all formats for FormatFloat ('b', 'e', 'E', 'f', 'g', 'G', 'x', 'X'). However, it seems like the 'b' format is not supported by ParseFloat (see [3]).

Is this correct? Is my code showing this correct?[3]
If Yes, is there some reason why the one format ('b') is not supported by ParseFloat?

My question is more one driven by curiosity rather than a need for this format. It was a surprise to me that one of the formats generated by the complement function in the same module was not supported.

Thanks,

Glen

[1]https://pkg.go.dev/strconv#FormatFloat

[2]https://pkg.go.dev/strconv#ParseFloat

[3]https://go.dev/play/p/b_GbyG_CFo6

[Kurtis Rader]

Note that the documentation for ParseFloat states: "ParseFloat accepts decimal and hexadecimal floating-point number syntax." In other words, it explicitly does not support the binary format emitted by FormatFloat('b'). I don't know why it doesn't but I'd bet that a review of old issues and changes to the source would probably shed some light on the reason.

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Kurtis Rader

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[Dan Kortschak]

On Thu, 2021-12-09 at 17:22 -0800, Kurtis Rader wrote:
> Note that the documentation for ParseFloat states: "ParseFloat
> accepts decimal and hexadecimal floating-point number syntax." In
> other words, it explicitly does not support the binary format emitted
> by FormatFloat('b'). I don't know why it doesn't but I'd bet that a
> review of old issues and changes to the source would probably shed
> some light on the reason.
>

This gives some background: https://github.com/golang/go/issues/12518

[Glen Newton]

Thanks to both of you for this! Appreciated.  :-)

Glen