Splitting CamelCaseWords in Go

[Tong Sun]

Hi, 

I need to split "CamelCaseWords" into individual words like "Camel Case Words". 

The following is the Perl code that I get for doing just that:

    @words = $words[0] =~ /[A-Z][^A-Z]*/g
        if @words == 1 && $words[0] =~ /^[A-Z]/;

However, I've been staring at it long enough to confirm myself that I really don't quite understand how it was done. 

Anyway, I'm wondering what's the neat way to do it in Go. 

PS. if you must know, I know that the algorithm I can borrow from is github.com/danverbraganza/varcaser, but when I was trying to use it, I noticed a side effect that makes it works for "myConstantVariable" but not for "GNU PYTHON Standard":

https://github.com/danverbraganza/varcaser/issues/1

Thanks

[Seth Bunce]

https://play.golang.org/p/-FM2wC22A0

My inclination would be to go for an approach like this. Then make a table-driven unit test and throw everything you can think of at it and iterate until you get what you need.

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[Tong Sun]

On Sun, Sep 3, 2017 at 6:05 PM, Seth Bunce wrote:

https://play.golang.org/p/-FM2wC22A0

Thanks a lot Seth!

FTR, I archived it in my personal treasure chest at

https://github.com/suntong/lang/blob/master/lang/Go/src/text/CamelCaseSplit.go

with a little bit enhancement. 

[Florian Florensen]

Hi, two approaches would be:

func camelAppend(str string) string {
  w := []rune(str)
  for i := len(w) - 1; i > 1; i-- {
    if unicode.IsUpper(w[i]) {
      w = append(w[:i], append([]rune{' '}, w[i:]...)...)
    }
  }
  return string(w)
}

func camelRegexp(str string) string {
  re := regexp.MustCompile(`([A-Z]+)`)
  str = re.ReplaceAllString(str, ` $1`)
  str = strings.Trim(str, " ")
  return str
}

$ go test -bench=.
goos: darwin
goarch: amd64
BenchmarkCamelAppend-4   3000000       444 ns/op
BenchmarkCamelRegexp-4    200000     11224 ns/op
PASS

[Tong Sun]

Oh thanks a lot Florian! 

I wished I had received it earlier (my email header said, Created at: Sun, Sep 3, 2017 at 6:03 PM (Delivered after 89531 seconds)), because my own version is embarrassingly complicated:

https://github.com/go-dedup/text/blob/3d0d998bef3db3937496933778c55e4f01cab5e4/text.go#L37-L60

I'll go with the simple camelRegexp, because to be fair, the camelAppend is not handing the cases that camelRegexp is handling, e.g., "FooBarBaz GNU PYTHON Standard", and I'll make it not inserting space if there is already one there...

PS. did you have to write extra code (not published here) to use `go test -bench=.`?

thx

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[Florian Florensen]

I've just joined the group and had to get activated, that's why my answer took so long. Should have waited until then.

Thank you for the notice! I fixed it in the playground: https://play.golang.org/p/kuk6FxesDq.

Although I wrote a benchmark (https://play.golang.org/p/YpnI257SHD), I didn't write tests. Sorry for that!

I still would use Seths version, since it correctly splits uppercase-words like CAMELCase to ["C" "A" "M" "E" "L" "Case"].

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[Tong Sun]

I'll be religiously avoiding "unicode.IsUpper()" as something mystery happened in the past:

https://groups.google.com/d/msg/golang-nuts/714WQs85H3w/KEqKgmAqAAAJ

BTW, for my case, I do need the string,

"FooBarBaz GNU PYTHON Standard"

to be split exactly to be

"Foo Bar Baz GNU PYTHON Standard"

I.e., 6 words altogether, no more spacing than this. 

thanks again for helping and showing me you benchmark code. 

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[Michael Jones]

Like this?

https://play.golang.org/p/OIE8jdWVGB

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[Tong Sun]

Almost, https://play.golang.org/p/6Zl_EKqFqT

But thanks a lot! It's significantly shorter/better than my initial version. 

[Steven Hartland]

Numbers don't match IsLower so how about:
https://play.golang.org/p/Z6q9dJZ7QK

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[Michael Jones]

Precisely, though probably a renaming is in order:

https://play.golang.org/p/AZ7Ptg4HYP

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[Steven Hartland]

You other option is:
splittable == v != ' ' && v == unicode.ToLower(v), depends what you want to happen with non-word characters?