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I'm playing with Go and run into something I'm unable to find in Google, although there is certainly something that exists:

I'm using the following struct:

type Syntax struct {
  name string
  extensions *regexp.Regexp

type Scanner struct {
  classifier * bayesian.Classifier
  save_file string
  name_to_syntax  map[string] *Syntax
  extensions_to_syntax  map[*regexp.Regexp] *Syntax

I'd like to perform the following using Go and I'm quoting ruby because it's how I'd do that using ruby:

test_regexpes = my_scanner.extensions_to_syntax.keys

My goal is to get an array of *regexp.Regexp .

Any idea on how to do that in a simple way ?

Thank you !

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2 Answers 2

up vote 1 down vote accepted

Maybe a better question for SO. For example, I think http://stackoverflow.com/questions/1841443/iterating-over-all-the-keys-of-a-golang-map is close to what you want. The only thing missing from that answer is allocating the slice. Here are the two parts together,

testRegexps := make(*regexp.Regexp, len(myScanner.extensionsToSyntax))
i := 0
for k := range myScanner.extensionsToSyntax {
    testRegexps[i] = k
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I wonder if there's a way to get this to approach the terseness of Ruby somehow more... –  rogerdpack Apr 22 '14 at 14:06

For followers, if you are "mapping" from an array/slice, it can be made more terse (in this case, from string to string):

here's an equivalent of #map!

array := []string{"a", "b", "c"};
for i, s := range array { array[i] = strings.ToUpper(s) }

and an equivalent of #map (NB: could map to a different array type here if desired)

array := []string{"a", "b", "c"};
array2 := make([]string, len(array))
for i, s := range array { array2[i] = strings.ToUpper(s) }

Alternatively you might be able to clean this up using some function pointers, and it would end up something like

array2 := _map(array, strings.ToUpper)

given this method

func _map(coll []string, f func(string) string) []string {
      var newColl = make([]string, len(coll))
      for i, s := range coll {
          newColl[i] = f(s)
      return newColl

There may be more ways to do this (libraries for the same?), such that you could get it down to something like

arr := arrays.StringArray([]string{"a", "b", "c"}).Map(func(v string) string { return strings.ToUpper(v) }); 

FWIW. test file: https://gist.github.com/anonymous/0de5f631a74c77a3da33

ref: https://groups.google.com/forum/#!topic/golang-nuts/fgaeXCUEPC4

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