[go-nuts] float exactness

['Jack Li' via golang-nuts]

Hi group,


1. 
Is there a package can do exact float operations, like Decimal in Python? For 
example:


x := 0.1; y := 0.2; z := x + y;


z will be exact 0.3


2.
Why literal operation is exact, variable is not?


fmt.Println(0.1 + 0.2) // 0.3 exactly


fmt.Println(x + y) // 0.30000000000000004




Thanks




func main() {
        x := 0.1
        y := 0.2
        fmt.Println("x + y  :", x   + y)
        fmt.Println("literal:", 0.1 + 0.2)


        x = 0.1
        y = 0.35
        fmt.Println("x + y  :", x   + y)
        fmt.Println("literal:", 0.1 + 0.35)
}


/*
$ go build && ./main
x + y  : 0.30000000000000004
literal: 0.3
x + y  : 0.44999999999999996
literal: 0.45
$ 
*/




// Python:


// >>> 0.1 + 0.2
// 0.30000000000000004


// >>> float(Decimal('0.1') + Decimal('0.2'))
// 0.3
// >>>


// >>> 0.35 + 0.1
// 0.44999999999999996


// >>> float(Decimal('0.35') + Decimal('0.1'))
// 0.45
// >>>

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