How to convert []string to []float64 in Golang?

Question

I'm new to programming, and trying to write a simple average program in Go.

package main

import (
    "fmt"
    "os"
)

var numbers []float64
var sum float64 = 0

func main() {

    if len(os.Args) > 1 {

        numbers = os.Args[1:]

    }

    fmt.Println("Numbers are: ", numbers)
    for _, value := range numbers {
        sum += value
    }

}

http://play.golang.org/p/TWNltPO71N

when I build the program, I got this error:

prog.go:15: cannot use os.Args[1:] (type []string) as type []float64 in assignment
[process exited with non-zero status]

So how to convert a slice of string to a slice of float numbers? Can I map a convert function to the slice?

tumdum · Accepted Answer · 2015-01-10 13:01:23Z

12

You need to convert string to float64 using strconv.ParseFloat function:

package main

import (
    "fmt"
    "os"
    "strconv"
)

var numbers []float64
var sum float64 = 0

func main() {

    if len(os.Args) <= 1 {
        return
    }

    for _, arg := range os.Args[1:] {
        if n, err := strconv.ParseFloat(arg, 64); err == nil {
            numbers = append(numbers, n)
        }
    }

    fmt.Println("Numbers are: ", numbers)
    for _, value := range numbers {
        sum += value
    }

}

edited Jan 10, 2015 at 13:01

answered Jan 10, 2015 at 11:16

tumdum

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4 Comments

fuz Over a year ago

I would not use append() here; the length of the array is known and we can just allocate it.

tumdum Over a year ago

Array size is know iff failed float parsing should 'abort' loop... I really don't like that you have changed the meaning of my code with your edit :/

fuz Over a year ago

Please undo my edit if you do not like it. It's okay.

Nick Over a year ago

Thank you very much. 1. for iterates over a slice is really simple yet useful. I guess this is the counterpart of map in a functional language. 2. strconv.ParseFloat not only convert the string to float, it also handles the separators - a mix use of comma and space, even irrelevant chars - strconv just done right. It's amazing! Go is simple and powerful.

ThinkChaos · Accepted Answer · 2015-01-10 11:19:59Z

2

It can't convert because string and int are not compatible.

Instead of having the numbers slice, just iterate over os.Args[1:], using ParseFloat from the strconv package.

fmt.Print("Numbers are: ")
for _, arg := range os.Args[1:] {
    fmt.Print(arg, " ")
    value, err := strconv.ParseFloat(arg, 64)
    if err != nil {
        panic(err)
    }
    sum += value
}

answered Jan 10, 2015 at 11:19

ThinkChaos

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