go slice

package main

import (
    "fmt"
)

type Pair struct {
    a int
    b int
}
type PairAndFreq struct {
    Pair
    Freq int
}

type PairSlice []PairAndFreq

type PairSliceSlice []PairSlice

func (pss PairSliceSlice) Weed() {
    fmt.Println(pss[0])
    weed(pss[0])
    fmt.Println(pss[0])
}

func weed(ps PairSlice) {

    m := make(map[Pair]int)

    for _, v := range ps {
        m[v.Pair]++
    }
    ps = ps[:0]
    for k, v := range m {

        ps = append(ps, PairAndFreq{k, v})

    }
    fmt.Println(ps)
}

func main() {

    pss := make(PairSliceSlice, 12)

    pss[0] = PairSlice{PairAndFreq{Pair{1, 1}, 1}, PairAndFreq{Pair{1, 1}, 1}}

    pss.Weed()
}

{1 1} 1} {{1 1} 1}]
[{{1 1} 2}]
[{{1 1} 2} {{1 1} 1}]