48 lines
916 B
Go
48 lines
916 B
Go
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// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import (
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"fmt"
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"strings"
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)
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type list []fmt.Stringer
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// list satisfies the fmt.Stringer
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func (l list) String() string {
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if len(l) == 0 {
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return "Sorry. We're waiting for delivery 🚚."
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}
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// use strings.Builder when you're combining unknown
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// list of strings together.
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var str strings.Builder
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for _, it := range l {
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// the builder doesn't know about the stringer interface.
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// that's why you need to call String method here.
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str.WriteString(it.String())
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str.WriteRune('\n')
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}
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return str.String()
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}
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func (l list) discount(ratio float64) {
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type discounter interface {
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discount(float64)
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}
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for _, it := range l {
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if it, ok := it.(discounter); ok {
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it.discount(ratio)
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}
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}
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}
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