带两位小数的 Float64

Question

I am new at this. I am trying to make a calculator that receives two numbers of type float64 but then I want to put the result of two decimals. I have been reading that it is with "%.2f" but it does not take well the result in fmt.Scanf

package main

import "fmt"

const menu string = "Calculator v1.0:\n\t1.a+b\n\t2.a-b\n\t3.a*b\n\t4.a/b\nSelect an option:"

func main() {
    var option int
    var firstNumber float64
    var secondNumber float64

    fmt.Println(menu)
    fmt.Scanf("%d", &option)

    fmt.Println("First number:")
    fmt.Scanf("%.2f", &firstNumber)
    fmt.Println("Second number:")
    fmt.Scanf("%.2f", &secondNumber)

    if option == 1 {
        println(sum(firstNumber, secondNumber))
    } else if option == 2 {
        println(subtract(firstNumber, secondNumber))
    } else if option == 3 {
        println(multiply(firstNumber, secondNumber))
    } else if option == 4 {
        println(divide(firstNumber, secondNumber))
    }

}

func sum(a float64, b float64) float64 {
    return a + b
}
func subtract(a float64, b float64) float64 {
    return a - b
}
func multiply(a float64, b float64) float64 {
    return a * b
}
func divide(a float64, b float64) float64 {
    return a / b
}

Answer 1

If you just need to accept a float 64 value for your inputs, you can simply use %f , or %g to set your values. The default precision is 6.

If you need greater precision and error handling, it may be more robust to bring your inputs in as strings, then parse and process them as you require.

Run the code below to see the inputs are both float64. The first will be output with a precision of 2, the second will be output with the default precision.

package main

import "fmt"

const menu string = "Calculator v1.0:\n\t1.a+b\n\t2.a-b\n\t3.a*b\n\t4.a/b\nSelect an option:"

func main() {
    var option int
    var firstNumber float64
    var secondNumber float64

    fmt.Println(menu)
    fmt.Scanf("%d", &option)

    fmt.Println("First number:")
    fmt.Scanf("%f", &firstNumber)
    fmt.Println("Second number:")
    fmt.Scanf("%g", &secondNumber)

    fmt.Printf("Input Type: %T, FirstNumber: %.2f\n", firstNumber, firstNumber)
    fmt.Printf("Input Type 2: %T, SecondNumber: %f\n", secondNumber, secondNumber)

    if option == 1 {
        println(sum(firstNumber, secondNumber))
    } else if option == 2 {
        println(subtract(firstNumber, secondNumber))
    } else if option == 3 {
        println(multiply(firstNumber, secondNumber))
    } else if option == 4 {
        println(divide(firstNumber, secondNumber))
    }

}

func sum(a float64, b float64) float64 {
    return a + b
}
func subtract(a float64, b float64) float64 {
    return a - b
}
func multiply(a float64, b float64) float64 {
    return a * b
}
func divide(a float64, b float64) float64 {
    return a / b
}