non_class.R

MulLayer <- function(){
  x_ <- NA
  y_ <- NA

  forward <- function(x, y){
    x_ <<- x
    y_ <<- y
    x * y
  }
  
  backward <- function(dout){
    dx <- dout * y
    dy <- dout * x
    list(dx = dx, dy = dy)
  }

  list(forward = forward, backward = backward, x = function() x_, y = function() y_)
}

m <- MulLayer()

print(m$x())
## [1] NA

m$forward(100, 2)

print(m$x())
## [1] 100