I recently tried appending two byte array slices in Go and came across some odd errors. My code is:
one:=make([]byte, 2)
two:=make([]byte, 2)
one[0]=0x00
one[1]=0x01
two[0]=0x02
two[1]=0x03
log.Printf("%X", append(one[:], two[:]))
three:=[]byte{0, 1}
four:=[]byte{2, 3}
five:=append(three, four)
And the errors are:
cannot use four (type []uint8) as type uint8 in append
cannot use two[:] (type []uint8) as type uint8 in append
Which taken into consideration the alleged robustness of Go's slices shouldn't be a problem:
http://code.google.com/p/go-wiki/wiki/SliceTricks
What am I doing wrong, and how should I go about appending two byte arrays?
The Go Programming Language Specification
Appending to and copying slices
The variadic function
append
appends zero or more valuesx
tos
of typeS
, which must be a slice type, and returns the resulting slice, also of typeS
. The valuesx
are passed to a parameter of type...T
whereT
is the element type ofS
and the respective parameter passing rules apply.
append(s S, x ...T) S // T is the element type of S
Passing arguments to
...
parametersIf the final argument is assignable to a slice type
[]T
, it may be passed unchanged as the value for a...T
parameter if the argument is followed by...
.
You need to use []T...
for the final argument.
For your example, with the final argument slice type []byte
, the argument is followed by ...
,
package main
import "fmt"
func main() {
one := make([]byte, 2)
two := make([]byte, 2)
one[0] = 0x00
one[1] = 0x01
two[0] = 0x02
two[1] = 0x03
fmt.Println(append(one[:], two[:]...))
three := []byte{0, 1}
four := []byte{2, 3}
five := append(three, four...)
fmt.Println(five)
}
Playground: https://play.golang.org/p/2jjXDc8_SWT
Output:
[0 1 2 3]
[0 1 2 3]