Get Multi-dimensional Array's element type in Swift

Question

I want custom Multi-dimensional Array in Swift. I declared MArray such like;

class MArray{
    private var flatten: [Any]
    private var shape: [Int]
    init(_ marray: [Any]){
         var shape: [Int] = []
         var marray: [Any] = marray
         (self.flatten, self.shape) = _call_flatten_row_major(&marray, &shape)
    }
}
fileprivate func _call_flatten_row_major(_ queue: inout [Any], _ shape: inout [Int]) -> (flatten: [Any], shape: [Int]){
    shape = [queue.count]
    return (_get_flatten_row_major(&queue, &shape), shape)
}
//breadth-first search
fileprivate func _get_flatten_row_major(_ queue: inout [Any], _ shape: inout [Int]) -> [Any]{
    precondition(shape.count == 1, "shape must have only one element")
    var cnt = 0 // count up the number that value is extracted from queue for while statement, reset 0 when iteration number reaches size
    var size = queue.count
    var axis = 0//the axis in searching

    while queue.count > 0 {
        //get first element
        let elements = queue[0]

        if let elements = elements as? [Any]{
            queue += elements

            if cnt == 0{ //append next dim
                shape.append(elements.count)
                axis += 1
            }
            else{// check if same dim is or not
                if shape[axis] != elements.count{
                    shape = shape.dropLast()
                }
            }
            cnt += 1
        }
        else{ // value was detected. this means queue in this case becomes flatten array
            break
        }
        //remove first element from array
        let _ = queue.removeFirst()

        if cnt == size{//reset count and forward next axis
            cnt = 0
            size *= shape[axis]
        }
    }

    return queue
}

However, as you can see, the argument of this MArray's initializer is [Any]. That is why MArray can't get flatten's type. Namely, MArray can't get Multi-dimensional Array's type.

Then, I used generics such like;

class MArray<T>{
    private var flatten: [T]
    private var shape: [Int]
    init(_ marray: [Any]){
         (self.flatten, self.shape): [T], [Int] = _call_flatten_row_major(&marray, &shape)
    }
}

and,

fileprivate func _call_flatten_row_major<T>(_ queue: inout [Any], _ shape: inout [Int]) -> (flatten: [T], shape: [Int]){
    shape = [queue.count]
    return (_get_flatten_row_major(&queue, &shape) as! [T], shape)
}

When I declared MArray<Int>([[1,2,3]]), it is OK. But when I declared MArray<Float>([[1,2,3]]),

Could not cast value of type 'Swift.Int' (0x7fff8b682600) to 'Swift.Float' (0x7fff8b6825e0).

I want Compiler to understand MArray<Float>([[1,2,3]])'s flatten type is Float.... (I should use ExpressibleByArrayLiteral??)

You may think that all I have to do is declaring MArray<Float>([[Float(1),Float(2),Float(3)]]). But Float(number) is annoying!!

Question

• How can I get multi-dimensional Array's element type?
• Should I use ExpressibleByArrayLiteral to achieve this? and if so, please tell me tips to use ExpressibleByArrayLiteral for Multi-dimensional Array...

For clawesome's answer

I tried Clawesome's answer, but compiler said

Type 'Float' does not conform to protocol 'ExpressibleByArrayLiteral'

clawesomes answer

code

Answer 1

You are declaring that you have an array of Floats with MArray<Float>. Instead you need to declare an array of an array of floats and the subsequently called functions must also be generacized. For your generic functions you just needed to have what T conforms to.

let mArray = MArray<Array<Float>>([[1,2,3]])

or

let mArray = MArray<[Float]>([[1,2,3]])

Class declaration:

class MArray<T: ExpressibleByArrayLiteral>{
    private var flatten: [T]
    private var shape: [Int] = [Int]()
    init(_ marray: [T]){
        // create temp var that can be passed by reference, let vars such 
        // as 'marray' cant be passed by reference unless declared as inout
        var temp = marray
        (self.flatten, self.shape) = _call_flatten_row_major(&temp, &shape)
    }
}

It can also be declared like the following:

class MArray<T> where T: ExpressibleByArrayLiteral {
    ...
}

Updated functions:

fileprivate func _call_flatten_row_major<T: ExpressibleByArrayLiteral>(_ queue: inout [T], _ shape: inout [Int]) -> (flatten: [T], shape: [Int]){
    shape = [queue.count]
    return (_get_flatten_row_major(&queue, &shape), shape)
}
//breadth-first search
fileprivate func _get_flatten_row_major<T: ExpressibleByArrayLiteral>(_ queue: inout [T], _ shape: inout [Int]) -> [T]{
    precondition(shape.count == 1, "shape must have only one element")
    var cnt = 0 // count up the number that value is extracted from queue for while statement, reset 0 when iteration number reaches size
    var size = queue.count
    var axis = 0//the axis in searching

    while queue.count > 0 {
        //get first element
        let elements = queue[0]

        if let elements = elements as? [T]{
            queue += elements

            if cnt == 0{ //append next dim
                shape.append(elements.count)
                axis += 1
            }
            else{// check if same dim is or not
                if shape[axis] != elements.count{
                    shape = shape.dropLast()
                }
            }
            cnt += 1
        }
        else{ // value was detected. this means queue in this case becomes flatten array
            break
        }
        //remove first element from array
        let _ = queue.removeFirst()

        if cnt == size{//reset count and forward next axis
            cnt = 0
            size *= shape[axis]
        }
    }

    return queue
}