75 lines
1.4 KiB
Go
75 lines
1.4 KiB
Go
// 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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// For more tutorials : https://learngoprogramming.com
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// In-person training : https://www.linkedin.com/in/inancgumus/
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// Follow me on twitter: https://twitter.com/inancgumus
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/*
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go run main.go < ./calculations.txt
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If you're not on Linux or OS X, etc but on Windows,
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Then, use Windows PowerShell to do the same thing.
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*/
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package main
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import (
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"bufio"
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"fmt"
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"os"
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"strings"
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)
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// After functions, you'll see that how we're going to refactor this
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// into a more readable version.
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func main() {
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const (
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promptChar = "> "
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errWrongOp = "%s operation is not supported\n"
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errWrongFormat = "operation is not recognized\n"
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usage = `
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usage: number operation number
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quit : type q to quit
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examples:
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3 + 5
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5 - 3
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`
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)
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fmt.Println(strings.TrimSpace(usage))
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for s := bufio.NewScanner(os.Stdin); ; {
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var (
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a, b, res float64
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op string
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)
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fmt.Print(promptChar, " ")
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if !s.Scan() {
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break
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}
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_, err := fmt.Sscanf(s.Text(), "%f %s %f", &a, &op, &b)
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if err != nil {
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fmt.Fprintf(os.Stderr, errWrongFormat)
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continue
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}
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switch op {
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case "+":
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res = a + b
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case "-":
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res = a - b
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default:
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fmt.Printf(errWrongOp, op)
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continue
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}
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fmt.Printf("%g %s %g = %g\n", a, op, b, res)
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}
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fmt.Println("bye.")
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}
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