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//Some additional utilities that are useful when processing CSV headers and data.
package utils
type Index map[string]int
// Return a map that maps each string in the input slice to its index in the slice.
func NewIndex(a []string) Index {
index := make(map[string]int)
for i, v := range a {
index[v] = i
}
return index
}
// Answer true if the index contains the specified string.
func (i Index) Contains(k string) bool {
_, ok := i[k]
return ok
}
// Calculate the intersection between two string slices. The first returned slice
// is the intersection between the two slices. The second returned slice is
// a slice of elements in the first slice but not the second. The third returned
// slice is a slice of elements in the second slice but not the first.
func Intersect(a []string, b []string) ([]string, []string, []string) {
index := NewIndex(a)
result := make([]string, 0, len(b))
aNotB := make([]string, len(a), len(a))
copy(aNotB, a)
bNotA := make([]string, 0, len(b))
for _, v := range b {
if i, ok := index[v]; ok {
result = append(result, v)
aNotB[i] = ""
} else {
bNotA = append(bNotA, v)
}
}
i := 0
for j := range a {
present := (aNotB[j] == a[j])
aNotB[i] = a[j]
if present {
i++
}
}
aNotB = aNotB[0:i]
return result, aNotB, bNotA
}
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