Go – Convert a float64 to an int in Go

How does one convert a float64 to an int in Go? I know the strconv package can be used to convert anything to or from a string, but not between data types where one isn't a string. I know I can use fmt.Sprintf to convert anything to a string, and then strconv it to the data type I need, but this extra conversion seems a bit clumsy – is there a better way to do this?

Best Answer

package main
import "fmt"
func main() {
  var x float64 = 5.7
  var y int = int(x)
  fmt.Println(y)  // outputs "5"
}

Related Solutions

Go – How to convert an int value to string in Go

Use the strconv package's Itoa function.

For example:

package main

import (
    "strconv"
    "fmt"
)

func main() {
    t := strconv.Itoa(123)
    fmt.Println(t)
}

You can concat strings simply by +'ing them, or by using the Join function of the strings package.

Go – Type converting slices of interfaces

In Go, there is a general rule that syntax should not hide complex/costly operations. Converting a string to an interface{} is done in O(1) time. Converting a []string to an interface{} is also done in O(1) time since a slice is still one value. However, converting a []string to an []interface{} is O(n) time because each element of the slice must be converted to an interface{}.

The one exception to this rule is converting strings. When converting a string to and from a []byte or a []rune, Go does O(n) work even though conversions are "syntax".

There is no standard library function that will do this conversion for you. You could make one with reflect, but it would be slower than the three line option.

Example with reflection:

func InterfaceSlice(slice interface{}) []interface{} {
    s := reflect.ValueOf(slice)
    if s.Kind() != reflect.Slice {
        panic("InterfaceSlice() given a non-slice type")
    }

    // Keep the distinction between nil and empty slice input
    if s.IsNil() {
        return nil
    }

    ret := make([]interface{}, s.Len())

    for i:=0; i<s.Len(); i++ {
        ret[i] = s.Index(i).Interface()
    }

    return ret
}

Your best option though is just to use the lines of code you gave in your question:

b := make([]interface{}, len(a))
for i := range a {
    b[i] = a[i]
}

Best Answer

Related Solutions

Go – How to convert an int value to string in Go

Go – Type converting slices of interfaces

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