main.go

package main

import (
	"fmt"
)

type SalaryCalculator interface {
	salaryCalculator() int
}

type Permanent struct {
	id    int
	basic int
	pf    int
}

type Contract struct {
	id    int
	basic int
}

func (p Permanent) salaryCalculator() int {
	return p.basic + p.pf
}

func (c Contract) salaryCalculator() int {
	return c.basic
}

func totalEx(s []SalaryCalculator) int {
	ex := 0

	for _, v := range s {
		ex = ex + v.salaryCalculator()
	}

	return ex
}

func main() {
	per1 := Permanent{1, 600, 100}
	per2 := Permanent{2, 600, 50}

	con1 := Contract{3, 300}

	total := []SalaryCalculator{per1, per2, con1}

	fmt.Println(totalEx(total))
}