{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Defining new types in Julia"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "mutable struct MyDiscreteWalker   # capital letters for each word in type name -- camel case\n",
    "    x::Int64\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "mutable struct SomethingElse   \n",
    "    x::Int64   # several fields\n",
    "    y::Float64\n",
    "    name::String\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "MyDiscreteWalker  # refers to the *type*"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 2 methods for type constructor:<ul><li> MyDiscreteWalker(x::<b>Int64</b>) in Main at In[1]:2</li> <li> MyDiscreteWalker(x) in Main at In[1]:2</li> </ul>"
      ],
      "text/plain": [
       "# 2 methods for type constructor:\n",
       "[1] MyDiscreteWalker(x::Int64) in Main at In[1]:2\n",
       "[2] MyDiscreteWalker(x) in Main at In[1]:2"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(MyDiscreteWalker)  # which methods / versions of a function exist"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Julia automatically created 2 **constructors** -- functions to create objects of that type"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(3)"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w = MyDiscreteWalker(3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "typeof(w)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3 + 4im"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "Complex(3, 4)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3 + 4im"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "3 + 4im  # im is i (sqrt of -1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "(::<b>Type{Complex}</b>)(re::<b>T</b>, im::<b>T</b>)<i> where T<:Real</i> in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/complex.jl#L12\" target=\"_blank\">complex.jl:12</a>"
      ],
      "text/plain": [
       "(::Type{Complex})(re::T, im::T) where T<:Real in Base at complex.jl:12"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "@which Complex(3, 4)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(3)"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "true"
      ]
     },
     "execution_count": 14,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w isa MyDiscreteWalker   # w is an **instance** of the type MyDiscreteWalker"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 2 methods for type constructor:<ul><li> MyDiscreteWalker(x::<b>Int64</b>) in Main at In[1]:2</li> <li> MyDiscreteWalker(x) in Main at In[1]:2</li> </ul>"
      ],
      "text/plain": [
       "# 2 methods for type constructor:\n",
       "[1] MyDiscreteWalker(x::Int64) in Main at In[1]:2\n",
       "[2] MyDiscreteWalker(x) in Main at In[1]:2"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(MyDiscreteWalker)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`MyDiscreteWalker(x::Int64)` is a method that works *only* when it receives an argument `x` of type `Int64`"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`MyDiscreteWalker(x)` will accept an `x` of any type"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "Any"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "Any"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "false"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "3.0 isa Int64"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "Float64"
      ]
     },
     "execution_count": 19,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "typeof(3.0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(3)"
      ]
     },
     "execution_count": 20,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "MyDiscreteWalker(3.0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "ename": "InexactError",
     "evalue": "InexactError: Int64(3.1)",
     "output_type": "error",
     "traceback": [
      "InexactError: Int64(3.1)",
      "",
      "Stacktrace:",
      " [1] Int64 at ./float.jl:710 [inlined]",
      " [2] convert at ./number.jl:7 [inlined]",
      " [3] MyDiscreteWalker(::Float64) at ./In[1]:2",
      " [4] top-level scope at In[21]:1"
     ]
    }
   ],
   "source": [
    "MyDiscreteWalker(3.1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3"
      ]
     },
     "execution_count": 22,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "Int64(3.0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "ename": "InexactError",
     "evalue": "InexactError: Int64(3.1)",
     "output_type": "error",
     "traceback": [
      "InexactError: Int64(3.1)",
      "",
      "Stacktrace:",
      " [1] Int64(::Float64) at ./float.jl:710",
      " [2] top-level scope at In[23]:1"
     ]
    }
   ],
   "source": [
    "Int64(3.1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3"
      ]
     },
     "execution_count": 24,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "trunc(Int64, 3.1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "floor(Int64, 3.1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3.0"
      ]
     },
     "execution_count": 26,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "floor(3.1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3"
      ]
     },
     "execution_count": 27,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "Int64(floor(3.1))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(3)"
      ]
     },
     "execution_count": 28,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w = MyDiscreteWalker(3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(3)"
      ]
     },
     "execution_count": 29,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Problem set 3:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Collecting information into one packet that belongs together: **encapsulation**"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "mutable struct Agent\n",
    "    infection_status::Int\n",
    "    num_infected::Int\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(3)"
      ]
     },
     "execution_count": 30,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w = MyDiscreteWalker(3)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "More common to use *immutable* structs:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "metadata": {},
   "outputs": [],
   "source": [
    "struct ExampleImmutable\n",
    "    x::Int\n",
    "    y::Int\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "z = ExampleImmutable()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3"
      ]
     },
     "execution_count": 32,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "convert(Int64, 3.0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {},
   "outputs": [
    {
     "ename": "InexactError",
     "evalue": "InexactError: Int64(3.1)",
     "output_type": "error",
     "traceback": [
      "InexactError: Int64(3.1)",
      "",
      "Stacktrace:",
      " [1] Int64 at ./float.jl:710 [inlined]",
      " [2] convert(::Type{Int64}, ::Float64) at ./number.jl:7",
      " [3] top-level scope at In[33]:1"
     ]
    }
   ],
   "source": [
    "convert(Int64, 3.1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3"
      ]
     },
     "execution_count": 34,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "Int64(3.0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "Int64(x::<b>Float64</b>) in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/float.jl#L707\" target=\"_blank\">float.jl:707</a>"
      ],
      "text/plain": [
       "Int64(x::Float64) in Base at float.jl:707"
      ]
     },
     "execution_count": 36,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "@which Int64(3.0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 37,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 14 methods for type constructor:<ul><li> Int64(x::<b>Union{Bool, Int32, Int64, UInt32, UInt64, UInt8, Int128, Int16, Int8, UInt128, UInt16}</b>) in Core at <a href=\"file:///Applications/Julia-1.4.app/Contents/Resources/julia/bin/../share/julia/base/boot.jl\" target=\"_blank\">boot.jl:707</a></li> <li> Int64(x::<b>Ptr</b>) in Core at <a href=\"file:///Applications/Julia-1.4.app/Contents/Resources/julia/bin/../share/julia/base/boot.jl\" target=\"_blank\">boot.jl:717</a></li> <li> Int64(x::<b>Float32</b>) in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/float.jl#L707\" target=\"_blank\">float.jl:707</a></li> <li> Int64(x::<b>Float64</b>) in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/float.jl#L707\" target=\"_blank\">float.jl:707</a></li> <li> (::<b>Type{T}</b>)(x::<b>Float16</b>)<i> where T<:Integer</i> in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/float.jl#L71\" target=\"_blank\">float.jl:71</a></li> <li> (::<b>Type{T}</b>)(z::<b>Complex</b>)<i> where T<:Real</i> in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/complex.jl#L37\" target=\"_blank\">complex.jl:37</a></li> <li> (::<b>Type{T}</b>)(x::<b>Rational</b>)<i> where T<:Integer</i> in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/rational.jl#L94\" target=\"_blank\">rational.jl:94</a></li> <li> (::<b>Type{T}</b>)(x::<b>BigInt</b>)<i> where T<:Union{Int128, Int16, Int32, Int64, Int8}</i> in Base.GMP at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/gmp.jl#L352\" target=\"_blank\">gmp.jl:352</a></li> <li> (::<b>Type{T}</b>)(x::<b>BigFloat</b>)<i> where T<:Integer</i> in Base.MPFR at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/mpfr.jl#L340\" target=\"_blank\">mpfr.jl:340</a></li> <li> (::<b>Type{T}</b>)(x::<b>T</b>)<i> where T<:Number</i> in Core at <a href=\"file:///Applications/Julia-1.4.app/Contents/Resources/julia/bin/../share/julia/base/boot.jl\" target=\"_blank\">boot.jl:715</a></li> <li> (::<b>Type{T}</b>)(x::<b>Base.TwicePrecision</b>)<i> where T<:Number</i> in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/twiceprecision.jl#L243\" target=\"_blank\">twiceprecision.jl:243</a></li> <li> (::<b>Type{T}</b>)(x::<b>AbstractChar</b>)<i> where T<:Union{AbstractChar, Number}</i> in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/char.jl#L50\" target=\"_blank\">char.jl:50</a></li> <li> (::<b>Type{T}</b>)(x::<b>Enum{T2}</b>)<i> where {T<:Integer, T2<:Integer}</i> in Base.Enums at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/Enums.jl#L19\" target=\"_blank\">Enums.jl:19</a></li> <li> (dt::<b>Type{#s662} where #s662<:Integer</b>)(ip::<b>Sockets.IPAddr</b>) in Sockets at <a href=\"file:///Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.4/Sockets/src/IPAddr.jl\" target=\"_blank\">/Applications/Julia-1.4.app/Contents/Resources/julia/share/julia/stdlib/v1.4/Sockets/src/IPAddr.jl:11</a></li> </ul>"
      ],
      "text/plain": [
       "# 14 methods for type constructor:\n",
       "[1] Int64(x::Union{Bool, Int32, Int64, UInt32, UInt64, UInt8, Int128, Int16, Int8, UInt128, UInt16}) in Core at boot.jl:707\n",
       "[2] Int64(x::Ptr) in Core at boot.jl:717\n",
       "[3] Int64(x::Float32) in Base at float.jl:707\n",
       "[4] Int64(x::Float64) in Base at float.jl:707\n",
       "[5] (::Type{T})(x::Float16) where T<:Integer in Base at float.jl:71\n",
       "[6] (::Type{T})(z::Complex) where T<:Real in Base at complex.jl:37\n",
       "[7] (::Type{T})(x::Rational) where T<:Integer in Base at rational.jl:94\n",
       "[8] (::Type{T})(x::BigInt) where T<:Union{Int128, Int16, Int32, Int64, Int8} in Base.GMP at gmp.jl:352\n",
       "[9] (::Type{T})(x::BigFloat) where T<:Integer in Base.MPFR at mpfr.jl:340\n",
       "[10] (::Type{T})(x::T) where T<:Number in Core at boot.jl:715\n",
       "[11] (::Type{T})(x::Base.TwicePrecision) where T<:Number in Base at twiceprecision.jl:243\n",
       "[12] (::Type{T})(x::AbstractChar) where T<:Union{AbstractChar, Number} in Base at char.jl:50\n",
       "[13] (::Type{T})(x::Enum{T2}) where {T<:Integer, T2<:Integer} in Base.Enums at Enums.jl:19\n",
       "[14] (dt::Type{#s662} where #s662<:Integer)(ip::Sockets.IPAddr) in Sockets at /Applications/Julia-1.4.app/Contents/Resources/julia/share/julia/stdlib/v1.4/Sockets/src/IPAddr.jl:11"
      ]
     },
     "execution_count": 37,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(Int64)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 39,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "convert(::<b>Type{T}</b>, x::<b>Number</b>)<i> where T<:Number</i> in Base at <a href=\"https://github.com/JuliaLang/julia/tree/b8e9a9ecc62ab49003bd4f1834771bdeb8cb1aa2/base/number.jl#L7\" target=\"_blank\">number.jl:7</a>"
      ],
      "text/plain": [
       "convert(::Type{T}, x::Number) where T<:Number in Base at number.jl:7"
      ]
     },
     "execution_count": 39,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "@which convert(Int64, 3.1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 41,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "ExampleImmutable(1, 2)"
      ]
     },
     "execution_count": 41,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "z = ExampleImmutable(1, 2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "1"
      ]
     },
     "execution_count": 42,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "z.x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "2"
      ]
     },
     "execution_count": 44,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "z.y"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "metadata": {},
   "outputs": [
    {
     "ename": "ErrorException",
     "evalue": "setfield! immutable struct of type ExampleImmutable cannot be changed",
     "output_type": "error",
     "traceback": [
      "setfield! immutable struct of type ExampleImmutable cannot be changed",
      "",
      "Stacktrace:",
      " [1] setproperty!(::ExampleImmutable, ::Symbol, ::Int64) at ./Base.jl:34",
      " [2] top-level scope at In[45]:1"
     ]
    }
   ],
   "source": [
    "z.x = 10"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "metadata": {},
   "outputs": [
    {
     "ename": "ErrorException",
     "evalue": "setfield! immutable struct of type ExampleImmutable cannot be changed",
     "output_type": "error",
     "traceback": [
      "setfield! immutable struct of type ExampleImmutable cannot be changed",
      "",
      "Stacktrace:",
      " [1] setproperty!(::ExampleImmutable, ::Symbol, ::Int64) at ./Base.jl:34",
      " [2] top-level scope at In[46]:1"
     ]
    }
   ],
   "source": [
    "z.y = 10"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Make walker move"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 47,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(3)"
      ]
     },
     "execution_count": 47,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w = MyDiscreteWalker(3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 48,
   "metadata": {},
   "outputs": [
    {
     "ename": "MethodError",
     "evalue": "MethodError: no method matching MyDiscreteWalker()\nClosest candidates are:\n  MyDiscreteWalker(!Matched::Int64) at In[1]:2\n  MyDiscreteWalker(!Matched::Any) at In[1]:2",
     "output_type": "error",
     "traceback": [
      "MethodError: no method matching MyDiscreteWalker()\nClosest candidates are:\n  MyDiscreteWalker(!Matched::Int64) at In[1]:2\n  MyDiscreteWalker(!Matched::Any) at In[1]:2",
      "",
      "Stacktrace:",
      " [1] top-level scope at In[48]:1"
     ]
    }
   ],
   "source": [
    "MyDiscreteWalker()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 49,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 2 methods for type constructor:<ul><li> MyDiscreteWalker(x::<b>Int64</b>) in Main at In[1]:2</li> <li> MyDiscreteWalker(x) in Main at In[1]:2</li> </ul>"
      ],
      "text/plain": [
       "# 2 methods for type constructor:\n",
       "[1] MyDiscreteWalker(x::Int64) in Main at In[1]:2\n",
       "[2] MyDiscreteWalker(x) in Main at In[1]:2"
      ]
     },
     "execution_count": 49,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(MyDiscreteWalker)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 50,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker"
      ]
     },
     "execution_count": 50,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "MyDiscreteWalker() = MyDiscreteWalker(0)  # outer constructor (lives outside definition of type)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 51,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 3 methods for type constructor:<ul><li> MyDiscreteWalker() in Main at In[50]:1</li> <li> MyDiscreteWalker(x::<b>Int64</b>) in Main at In[1]:2</li> <li> MyDiscreteWalker(x) in Main at In[1]:2</li> </ul>"
      ],
      "text/plain": [
       "# 3 methods for type constructor:\n",
       "[1] MyDiscreteWalker() in Main at In[50]:1\n",
       "[2] MyDiscreteWalker(x::Int64) in Main at In[1]:2\n",
       "[3] MyDiscreteWalker(x) in Main at In[1]:2"
      ]
     },
     "execution_count": 51,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(MyDiscreteWalker)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 52,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(0)"
      ]
     },
     "execution_count": 52,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w = MyDiscreteWalker()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Now make it move"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 53,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "jump! (generic function with 1 method)"
      ]
     },
     "execution_count": 53,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function jump!(w::MyDiscreteWalker)\n",
    "    w.x += rand( (-1, +1) )\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 54,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "pos (generic function with 1 method)"
      ]
     },
     "execution_count": 54,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "pos(w::MyDiscreteWalker) = w.x   # getter function"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "w.x   # w.<TAB>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 55,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(:x,)"
      ]
     },
     "execution_count": 55,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "propertynames(w)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 59,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(:x, :y)"
      ]
     },
     "execution_count": 59,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "propertynames(z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 60,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0"
      ]
     },
     "execution_count": 60,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "pos(w)   # interface to my object; removes me from the internal details"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 61,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "set_pos! (generic function with 1 method)"
      ]
     },
     "execution_count": 61,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function set_pos!(w, x)   # setter function\n",
    "    w.x = x\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 62,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "jump (generic function with 1 method)"
      ]
     },
     "execution_count": 62,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "jump(MyDiscreteWalker) = rand( (-1, +1) )"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "function jump!(w::MyDiscreteWalker)\n",
    "    old_pos = pos(w)\n",
    "    set_pos!(old_pos + jump(w))\n",
    "end"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In this version of `jump!`, I never refer to internal details of the object."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 64,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "walk! (generic function with 1 method)"
      ]
     },
     "execution_count": 64,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function walk!(w::MyDiscreteWalker, N)\n",
    "    for i in 1:N\n",
    "        jump!(w)\n",
    "    end\n",
    "    \n",
    "    return w\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 65,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(0)"
      ]
     },
     "execution_count": 65,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 66,
   "metadata": {},
   "outputs": [
    {
     "ename": "MethodError",
     "evalue": "MethodError: no method matching walk!(::Int64)\nClosest candidates are:\n  walk!(!Matched::MyDiscreteWalker, !Matched::Any) at In[64]:2",
     "output_type": "error",
     "traceback": [
      "MethodError: no method matching walk!(::Int64)\nClosest candidates are:\n  walk!(!Matched::MyDiscreteWalker, !Matched::Any) at In[64]:2",
      "",
      "Stacktrace:",
      " [1] top-level scope at In[66]:1"
     ]
    }
   ],
   "source": [
    "walk!(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 67,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "walk! (generic function with 1 method)"
      ]
     },
     "execution_count": 67,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "walk!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 68,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 1 method for generic function <b>walk!</b>:<ul><li> walk!(w::<b>MyDiscreteWalker</b>, N) in Main at In[64]:2</li> </ul>"
      ],
      "text/plain": [
       "# 1 method for generic function \"walk!\":\n",
       "[1] walk!(w::MyDiscreteWalker, N) in Main at In[64]:2"
      ]
     },
     "execution_count": 68,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(walk!)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 69,
   "metadata": {},
   "outputs": [
    {
     "ename": "UndefVarError",
     "evalue": "UndefVarError: aweirdfunction not defined",
     "output_type": "error",
     "traceback": [
      "UndefVarError: aweirdfunction not defined",
      "",
      "Stacktrace:",
      " [1] top-level scope at In[69]:1"
     ]
    }
   ],
   "source": [
    "aweirdfunction(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 70,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(4)"
      ]
     },
     "execution_count": 70,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "walk!(w, 10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 71,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyDiscreteWalker(4)"
      ]
     },
     "execution_count": 71,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w  # has been mutated / modified"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Continuous walkers"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 72,
   "metadata": {},
   "outputs": [],
   "source": [
    "mutable struct MyContinuousWalker\n",
    "    y::Float64\n",
    "end "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 73,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyContinuousWalker(3.0)"
      ]
     },
     "execution_count": 73,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w = MyContinuousWalker(3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 74,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "true"
      ]
     },
     "execution_count": 74,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w isa MyContinuousWalker"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 75,
   "metadata": {},
   "outputs": [
    {
     "ename": "MethodError",
     "evalue": "MethodError: no method matching jump!(::MyContinuousWalker)\nClosest candidates are:\n  jump!(!Matched::MyDiscreteWalker) at In[53]:2",
     "output_type": "error",
     "traceback": [
      "MethodError: no method matching jump!(::MyContinuousWalker)\nClosest candidates are:\n  jump!(!Matched::MyDiscreteWalker) at In[53]:2",
      "",
      "Stacktrace:",
      " [1] top-level scope at In[75]:1"
     ]
    }
   ],
   "source": [
    "jump!(w)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 76,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 1 method for generic function <b>jump!</b>:<ul><li> jump!(w::<b>MyDiscreteWalker</b>) in Main at In[53]:2</li> </ul>"
      ],
      "text/plain": [
       "# 1 method for generic function \"jump!\":\n",
       "[1] jump!(w::MyDiscreteWalker) in Main at In[53]:2"
      ]
     },
     "execution_count": 76,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(jump!)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 77,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "jump (generic function with 2 methods)"
      ]
     },
     "execution_count": 77,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "jump(w::MyContinuousWalker) = randn()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 78,
   "metadata": {},
   "outputs": [
    {
     "ename": "MethodError",
     "evalue": "MethodError: no method matching jump!(::MyContinuousWalker)\nClosest candidates are:\n  jump!(!Matched::MyDiscreteWalker) at In[53]:2",
     "output_type": "error",
     "traceback": [
      "MethodError: no method matching jump!(::MyContinuousWalker)\nClosest candidates are:\n  jump!(!Matched::MyDiscreteWalker) at In[53]:2",
      "",
      "Stacktrace:",
      " [1] top-level scope at In[78]:1"
     ]
    }
   ],
   "source": [
    "jump!(w::MyContinuousWalker)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 79,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 1 method for generic function <b>jump!</b>:<ul><li> jump!(w::<b>MyDiscreteWalker</b>) in Main at In[53]:2</li> </ul>"
      ],
      "text/plain": [
       "# 1 method for generic function \"jump!\":\n",
       "[1] jump!(w::MyDiscreteWalker) in Main at In[53]:2"
      ]
     },
     "execution_count": 79,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(jump!)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 89,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "jump! (generic function with 2 methods)"
      ]
     },
     "execution_count": 89,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function jump!(w)  # takes argument w of *any* type\n",
    "    old_pos = pos(w)\n",
    "    set_pos!(w, old_pos + jump(w))\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 81,
   "metadata": {},
   "outputs": [
    {
     "ename": "MethodError",
     "evalue": "MethodError: no method matching pos(::Int64)\nClosest candidates are:\n  pos(!Matched::MyDiscreteWalker) at In[54]:1",
     "output_type": "error",
     "traceback": [
      "MethodError: no method matching pos(::Int64)\nClosest candidates are:\n  pos(!Matched::MyDiscreteWalker) at In[54]:1",
      "",
      "Stacktrace:",
      " [1] jump!(::Int64) at ./In[80]:2",
      " [2] top-level scope at In[81]:1"
     ]
    }
   ],
   "source": [
    "jump!(1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 83,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyContinuousWalker(3.0)"
      ]
     },
     "execution_count": 83,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 84,
   "metadata": {},
   "outputs": [
    {
     "ename": "MethodError",
     "evalue": "MethodError: no method matching pos(::MyContinuousWalker)\nClosest candidates are:\n  pos(!Matched::MyDiscreteWalker) at In[54]:1",
     "output_type": "error",
     "traceback": [
      "MethodError: no method matching pos(::MyContinuousWalker)\nClosest candidates are:\n  pos(!Matched::MyDiscreteWalker) at In[54]:1",
      "",
      "Stacktrace:",
      " [1] jump!(::MyContinuousWalker) at ./In[82]:2",
      " [2] top-level scope at In[84]:1"
     ]
    }
   ],
   "source": [
    "jump!(w)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 85,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 1 method for generic function <b>pos</b>:<ul><li> pos(w::<b>MyDiscreteWalker</b>) in Main at In[54]:1</li> </ul>"
      ],
      "text/plain": [
       "# 1 method for generic function \"pos\":\n",
       "[1] pos(w::MyDiscreteWalker) in Main at In[54]:1"
      ]
     },
     "execution_count": 85,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(pos)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 86,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "pos (generic function with 2 methods)"
      ]
     },
     "execution_count": 86,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "pos(w::MyContinuousWalker) = w.y"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 87,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "set_pos! (generic function with 2 methods)"
      ]
     },
     "execution_count": 87,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function set_pos!(w::MyContinuousWalker, pos)\n",
    "    w.y = pos\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 90,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "2.1822730537401607"
      ]
     },
     "execution_count": 90,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "jump!(w)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 91,
   "metadata": {},
   "outputs": [
    {
     "ename": "MethodError",
     "evalue": "MethodError: no method matching walk!(::MyContinuousWalker, ::Int64)\nClosest candidates are:\n  walk!(!Matched::MyDiscreteWalker, ::Any) at In[64]:2",
     "output_type": "error",
     "traceback": [
      "MethodError: no method matching walk!(::MyContinuousWalker, ::Int64)\nClosest candidates are:\n  walk!(!Matched::MyDiscreteWalker, ::Any) at In[64]:2",
      "",
      "Stacktrace:",
      " [1] top-level scope at In[91]:1"
     ]
    }
   ],
   "source": [
    "walk!(w, 10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 92,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 1 method for generic function <b>walk!</b>:<ul><li> walk!(w::<b>MyDiscreteWalker</b>, N) in Main at In[64]:2</li> </ul>"
      ],
      "text/plain": [
       "# 1 method for generic function \"walk!\":\n",
       "[1] walk!(w::MyDiscreteWalker, N) in Main at In[64]:2"
      ]
     },
     "execution_count": 92,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(walk!)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 93,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "walk! (generic function with 2 methods)"
      ]
     },
     "execution_count": 93,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function walk!(w, N)\n",
    "    for i in 1:N\n",
    "        jump!(w)\n",
    "    end\n",
    "    \n",
    "    return w\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 94,
   "metadata": {},
   "outputs": [
    {
     "ename": "MethodError",
     "evalue": "MethodError: no method matching pos(::Int64)\nClosest candidates are:\n  pos(!Matched::MyContinuousWalker) at In[86]:1\n  pos(!Matched::MyDiscreteWalker) at In[54]:1",
     "output_type": "error",
     "traceback": [
      "MethodError: no method matching pos(::Int64)\nClosest candidates are:\n  pos(!Matched::MyContinuousWalker) at In[86]:1\n  pos(!Matched::MyDiscreteWalker) at In[54]:1",
      "",
      "Stacktrace:",
      " [1] jump!(::Int64) at ./In[89]:2",
      " [2] walk!(::Int64, ::Int64) at ./In[93]:3",
      " [3] top-level scope at In[94]:1"
     ]
    }
   ],
   "source": [
    "walk!(1, 2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 95,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyContinuousWalker(-3.3119507350317736)"
      ]
     },
     "execution_count": 95,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "walk!(w, 10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 96,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "MyContinuousWalker(-3.3119507350317736)"
      ]
     },
     "execution_count": 96,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Abstract types"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "\"A discrete walker is a **kind of** walker\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 98,
   "metadata": {},
   "outputs": [],
   "source": [
    "abstract type RandomWalker end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 99,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "RandomWalker"
      ]
     },
     "execution_count": 99,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "RandomWalker"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 100,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "# 0 methods for type constructor:<ul></ul>"
      ],
      "text/plain": [
       "# 0 methods for type constructor:"
      ]
     },
     "execution_count": 100,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "methods(RandomWalker)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 101,
   "metadata": {},
   "outputs": [],
   "source": [
    "mutable struct DiscreteWalker <: RandomWalker\n",
    "    x::Int64\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 102,
   "metadata": {},
   "outputs": [],
   "source": [
    "mutable struct ContinuousWalker <: RandomWalker\n",
    "    y::Int64\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 103,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "pos (generic function with 4 methods)"
      ]
     },
     "execution_count": 103,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "pos(w::DiscreteWalker) = w.x\n",
    "pos(w::ContinuousWalker) = w.y"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 104,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "walk! (generic function with 3 methods)"
      ]
     },
     "execution_count": 104,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "function walk!(w::RandomWalker, N)\n",
    "    for i in 1:N\n",
    "        jump!(w)\n",
    "    end\n",
    "    \n",
    "    return w\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 105,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "DiscreteWalker(10)"
      ]
     },
     "execution_count": 105,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w = DiscreteWalker(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 106,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "true"
      ]
     },
     "execution_count": 106,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w isa DiscreteWalker"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 107,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "true"
      ]
     },
     "execution_count": 107,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "w isa RandomWalker"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 108,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "2-element Array{DiscreteWalker,1}:\n",
       " DiscreteWalker(1)\n",
       " DiscreteWalker(2)"
      ]
     },
     "execution_count": 108,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "[DiscreteWalker(1), DiscreteWalker(2)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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