Go: Define multidimensional array with existing array's type and values?

Question

Is it possible to a)define b)initialize a new multidimensional array using an existing array, like in following code instead of var b [2][3]int, just saying something like var b [2]a ?
Using a's type whatever it is, instead of hardcoding it (which misses the point of using [...] for a).
And perhaps handling initialization=copying of values at the same time?

package main

func main () {
        a := [...]int{4,5,6}
        var b [2][3]int
        b[0],b[1] = a,a 
}

(I'm aware of ease and convenience of slices, but this question is about understanding arrays.)

Edit: can't believe I forgot about var b [2][len(a)]int, beginner's brain freeze. One line answer would be var b = [2][len(a)]int{a,a} . That's a type conversion, right?

maybe Templates since they can support any type

nathan hayfield
– nathan hayfield

2012-11-20 00:34:04 +00:00
Commented Nov 20, 2012 at 0:34 — nathan hayfield
– nathan hayfield, Commented Nov 20, 2012 at 0:34

Stephen Weinberg · Accepted Answer · 2012-11-20 00:43:41Z

5

The following code would also work. Both your example and mine do the same thing and neither should be much faster than the other.

Unless you use reflect to make a slice (not array) of your [3]int, it is impossible to not repeat [3]int in your new type. Even that is not possible in the current release. It is in tip and will be released in Go 1.1.

package main

import "fmt"

func main() {
    a := [...]int{4,5,6}
    var b = [2][3]int{a, a}
    fmt.Println(b)
}

edited Nov 20, 2012 at 0:43

answered Nov 20, 2012 at 0:38

Stephen Weinberg

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2 Comments

kilves76 Over a year ago

Thank you! I also seem to have a beginner's brain freeze, as var b [2][len(a)]int seems to work just fine.

Stephen Weinberg Over a year ago

Yes, len(array) is a constant expression (calculated at compile time) and therefore can be used when defining other array types.

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