{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "mutable struct MulLayer\n",
    "    x\n",
    "    y\n",
    "    (::Type{MulLayer})() = new()\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "forward (generic function with 1 method)"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function forward(self::MulLayer, x, y)\n",
    "    self.x = x\n",
    "    self.y = y\n",
    "    out = x * y\n",
    "    return out\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "backward (generic function with 1 method)"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function backward(self::MulLayer, dout)\n",
    "    dx = dout * self.y\n",
    "    dy = dout * self.x\n",
    "    return dx, dy\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "1.1"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "apple = 100\n",
    "apple_num = 2\n",
    "tax = 1.1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MulLayer(#undef, #undef)"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "mul_apple_layer = MulLayer()\n",
    "mul_tax_layer = MulLayer()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "220.00000000000003"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "apple_price = forward(mul_apple_layer, apple, apple_num)\n",
    "price = forward(mul_tax_layer, apple_price, tax)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(2.2, 110.00000000000001, 200)"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dprice = 1\n",
    "dapple_price, dtax = backward(mul_tax_layer, dprice)\n",
    "dapple, dapple_num = backward(mul_apple_layer, dapple_price)\n",
    "(dapple, dapple_num, dtax)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "backward (generic function with 2 methods)"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "mutable struct AddLayer end\n",
    "\n",
    "function forward(self::AddLayer, x, y)\n",
    "    out = x + y\n",
    "    return out\n",
    "end    \n",
    "    \n",
    "function backward(self::AddLayer, dout)\n",
    "    dx = dout * 1\n",
    "    dy = dout * 1\n",
    "    return dx, dy\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "1.1"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "apple = 100\n",
    "apple_num = 2\n",
    "orange = 150\n",
    "orange_num = 3\n",
    "tax = 1.1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MulLayer(#undef, #undef)"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "mul_apple_layer = MulLayer()\n",
    "mul_orange_layer = MulLayer()\n",
    "add_apple_orange_layer = AddLayer()\n",
    "mul_tax_layer = MulLayer()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "715.0000000000001"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "apple_price = forward(mul_apple_layer, apple, apple_num)\n",
    "orange_price = forward(mul_orange_layer, orange, orange_num)\n",
    "all_price = forward(add_apple_orange_layer, apple_price, orange_price)\n",
    "price = forward(mul_tax_layer, all_price, tax)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(2.2, 110.00000000000001, 3.3000000000000003, 165.0, 650)"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dprice = 1\n",
    "dall_price, dtax = backward(mul_tax_layer, dprice)\n",
    "dapple_price, dorange_price = backward(add_apple_orange_layer, dall_price)\n",
    "dorange, dorange_num = backward(mul_orange_layer, dorange_price)\n",
    "dapple, dapple_num = backward(mul_apple_layer, dapple_price)\n",
    "(dapple, dapple_num, dorange, dorange_num, dtax)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  }
 ],
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