text: package yaml
  
  import (
  	"reflect"
  	"unicode"
  )
  
  type keyList []reflect.Value
  
  func (l keyList) Len() int      { return len(l) }
  func (l keyList) Swap(i, j int) { l[i], l[j] = l[j], l[i] }
  func (l keyList) Less(i, j int) bool {
  	a := l[i]
  	b := l[j]
  	ak := a.Kind()
  	bk := b.Kind()
  	for (ak == reflect.Interface || ak == reflect.Ptr) && !a.IsNil() {
  		a = a.Elem()
  		ak = a.Kind()
  	}
  	for (bk == reflect.Interface || bk == reflect.Ptr) && !b.IsNil() {
  		b = b.Elem()
  		bk = b.Kind()
  	}
  	af, aok := keyFloat(a)
  	bf, bok := keyFloat(b)
  	if aok && bok {
  		if af != bf {
  			return af < bf
  		}
  		if ak != bk {
  			return ak < bk
  		}
  		return numLess(a, b)
  	}
  	if ak != reflect.String || bk != reflect.String {
  		return ak < bk
  	}
  	ar, br := []rune(a.String()), []rune(b.String())
  	for i := 0; i < len(ar) && i < len(br); i++ {
  		if ar[i] == br[i] {
  			continue
  		}
  		al := unicode.IsLetter(ar[i])
  		bl := unicode.IsLetter(br[i])
  		if al && bl {
  			return ar[i] < br[i]
  		}
  		if al || bl {
  			return bl
  		}
  		var ai, bi int
  		var an, bn int64
  		if ar[i] == '0' || br[i] == '0' {
  			for j := i-1; j >= 0 && unicode.IsDigit(ar[j]); j-- {
  				if ar[j] != '0' {
  					an = 1
  					bn = 1
  					break
  				}
  			}
  		}
  		for ai = i; ai < len(ar) && unicode.IsDigit(ar[ai]); ai++ {
  			an = an*10 + int64(ar[ai]-'0')
  		}
  		for bi = i; bi < len(br) && unicode.IsDigit(br[bi]); bi++ {
  			bn = bn*10 + int64(br[bi]-'0')
  		}
  		if an != bn {
  			return an < bn
  		}
  		if ai != bi {
  			return ai < bi
  		}
  		return ar[i] < br[i]
  	}
  	return len(ar) < len(br)
  }
  
  // keyFloat returns a float value for v if it is a number/bool
  // and whether it is a number/bool or not.
  func keyFloat(v reflect.Value) (f float64, ok bool) {
  	switch v.Kind() {
  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
  		return float64(v.Int()), true
  	case reflect.Float32, reflect.Float64:
  		return v.Float(), true
  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
  		return float64(v.Uint()), true
  	case reflect.Bool:
  		if v.Bool() {
  			return 1, true
  		}
  		return 0, true
  	}
  	return 0, false
  }
  
  // numLess returns whether a < b.
  // a and b must necessarily have the same kind.
  func numLess(a, b reflect.Value) bool {
  	switch a.Kind() {
  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
  		return a.Int() < b.Int()
  	case reflect.Float32, reflect.Float64:
  		return a.Float() < b.Float()
  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
  		return a.Uint() < b.Uint()
  	case reflect.Bool:
  		return !a.Bool() && b.Bool()
  	}
  	panic("not a number")
  }
  