Go Golang：自定义类型上的类型断言

Question

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

I am practicing sort using heap but

  prog.go:85: type bucket is not an expression
  prog.go:105: cannot use heap.Pop(bucket[i].([]IntArr)) (type interface {}) as type int in assignment: need type assertion
  [process exited with non-zero status]

I am getting those errors and can't figure out how to type assert properly

The problem is from the lines:

  heap.Push(bucket[x].([]IntArr), elem)

  arr[index] = heap.Pop(bucket[i].([]IntArr))

Because I want to use heap structure in order to extract values from each bucket

And each bucket is []IntArr

And IntArr is []int like the following

type IntArr []int
type bucket [10]IntArr

I have been trying many ways over the weekend and can't figure out, I greatly appreciate it.

Answer 1

From go spec :

For an expression x of interface type and a type T, the primary expression

x.(T)

asserts that x is not nil and that the value stored in x is of type T. The notation x.(T) is called a type assertion.

bucket[x] is not an expression of an interface type, see more here .

Answer 2

To use heap package you should implement heap.Interface for your type (in this case, for your IntArr type). You can find example here: http://golang.org/pkg/container/heap/#pkg-examples

Then you can do things like

heap.Push(bucket[x], elem)