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#light

// some possibilities
// (1) use Array.init

let project1 j a = Array.init (Array2.length1 a) (fun i -> a.[i,j])
let project2 i a = Array.init (Array2.length2 a) (fun j -> a.[i,j])

// (2) use a sequence expression / list comprehension
let project1' j a = [|for i in 0 .. Array2.length1 a-1 -> a.[i,j]|]
let project2' i a = [|for j in 0 .. Array2.length2 a-1 -> a.[i,j]|]

// note that it doesn't really seem worth factoring out the common pattern but it's possible

let project funLen funVarFix fixIndex a = 
    Array.init (funLen a) (fun varIndex -> let i,j = funVarFix varIndex fixIndex in Array2.get a i j)

// val project : ('a [,] -> int) -> (int -> 'b -> int * int) -> 'b -> 'a [,] -> 'a array

let project1'' j a = project Array2.length1 (fun i j -> i,j) j a
let project2'' i a = project Array2.length2 (fun j i -> i,j) i a
let a = Array2.init 3 5 (fun i j -> i*i+j)

// val it : int [,] = [|[|0; 1; 2; 3; 4|]; [|1; 2; 3; 4; 5|]; [|4; 5; 6; 7; 8|]|]

project1 2 a
project1' 2 a
project1'' 2 a

// val it : int array = [|2; 3; 6|]

project2 2 a
project2' 2 a
project2'' 2 a

// val it : int array = [|4; 5; 6; 7; 8|]