SparseVector[A] = ref object
  N*: int32
  indices*: seq[int32]
  vals*: seq[A]

SparseMatrixKind = enum
  CSR, CSC, COO

SparseMatrixObj[A] = object
  kind*: SparseMatrixKind
  M*, N*, nnz*: int32
  rows*, cols*: seq[int32]
  vals*: seq[A]

SparseMatrix[A] = ref SparseMatrixObj[A]

proc len(v: SparseVector): int {...}{.inline.}

proc nnz(v: SparseVector): int32 {...}{.inline.}

proc rowLen(m: SparseMatrix): int32

proc colLen(m: SparseMatrix): int32

proc sparseVector[A](N: int32; indices: seq[int32]; vals: seq[A]): SparseVector[A]

proc sparseMatrix[A: Scalar](kind: SparseMatrixKind; M, N, nnz: int32;
                           rows, cols: seq[int32]; vals: seq[A]): SparseMatrix[A]

proc csr[A: Scalar](rows, cols: seq[int32]; vals: seq[A]; numCols: int32): SparseMatrix[A]

proc csc[A: Scalar](rows, cols: seq[int32]; vals: seq[A]; numRows: int32): SparseMatrix[A]

proc coo[A: Scalar](rows, cols: seq[int32]; vals: seq[A]; numRows, numCols: int32): SparseMatrix[
    A]

proc dense[A](v: SparseVector[A]): Vector[A]

proc dense[A](m: SparseMatrix[A]; order = colMajor): Matrix[A]

proc `==`[A](v, w: SparseVector[A]): bool

proc `==`[A](m, n: SparseMatrix[A]): bool

proc `$`[A](v: SparseVector[A]): string

proc `$`[A](m: SparseMatrix[A]): string

iterator items[A](v: SparseVector[A]): A

iterator pairs[A](v: SparseVector[A]): tuple[key: int32, val: A]

iterator nonzero[A](v: SparseVector[A]): tuple[key: int32, val: A]

iterator items[A](m: SparseMatrix[A]): A

iterator pairs[A](m: SparseMatrix[A]): tuple[key: (int32, int32), val: A]

iterator nonzero[A](m: SparseMatrix[A]): tuple[key: (int32, int32), val: A]