diff --git a/docs/notebooks/BigInts.ipynb b/docs/notebooks/BigInts.ipynb
index a600c95..7633eb9 100644
--- a/docs/notebooks/BigInts.ipynb
+++ b/docs/notebooks/BigInts.ipynb
@@ -2,14 +2,16 @@
  "cells": [
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 51,
    "id": "73967878",
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
-     "text": []
+     "text": [
+      "[0 3 1]"
+     ]
     }
    ],
    "source": [
@@ -19,14 +21,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 52,
    "id": "b34d58ef",
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
-     "text": []
+     "text": [
+      "[0 3 1]"
+     ]
     }
    ],
    "source": [
@@ -47,7 +51,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "956c8ee2",
+   "id": "3f77ce91",
    "metadata": {},
    "source": [
     "## Take Two\n",
@@ -58,341 +62,23 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "afe33f94",
+   "id": "b2845a8d",
    "metadata": {},
    "outputs": [],
    "source": []
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "id": "03a44beb",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "9947b864",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "e91b6e37",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "8e7d4379",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "211669e7",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "d7ee0e4a",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "c9f34050",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "9d5972c4",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "cd6dc2e4",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "0beeac21",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "ccc32d74",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "7d2c5b56",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "83cbf474",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "be9be8d9",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "4c7df3f0",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "88f27acd",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "960edfef",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "2b3cad6c",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "7c613941",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "991f0d25",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "c3221039",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "ff5ab28c",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "58a46766",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "f488664c",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "5eefa527",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "d1f695de",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "22e5236c",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "5e069159",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "8e2fc444",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "025672cb",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "3359c82f",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "011563c0",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "f0e5eb9a",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "cb5a858d",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "936ef79c",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "e8a8bbe9",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "80672bab",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "aa635304",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "eba35315",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "14e8ca33",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 53,
    "id": "35476eac",
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
-     "text": []
+     "text": [
+      "[0 3 1]"
+     ]
     }
    ],
    "source": [
@@ -401,7 +87,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 54,
    "id": "02a48806",
    "metadata": {},
    "outputs": [
@@ -420,7 +106,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 55,
    "id": "1d276daf",
    "metadata": {},
    "outputs": [
@@ -440,7 +126,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 56,
    "id": "2454e662",
    "metadata": {},
    "outputs": [
@@ -469,7 +155,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 57,
    "id": "8a60b54b",
    "metadata": {},
    "outputs": [
@@ -509,7 +195,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 58,
    "id": "3fc98ccd",
    "metadata": {},
    "outputs": [
@@ -529,7 +215,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 59,
    "id": "b838c4cb",
    "metadata": {},
    "outputs": [
@@ -555,7 +241,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 60,
    "id": "faaac9d6",
    "metadata": {},
    "outputs": [
@@ -576,7 +262,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 61,
    "id": "2a613f36",
    "metadata": {},
    "outputs": [
@@ -598,7 +284,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 62,
    "id": "e97b149d",
    "metadata": {},
    "outputs": [
@@ -619,7 +305,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 63,
    "id": "de4fe588",
    "metadata": {},
    "outputs": [
@@ -637,7 +323,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 64,
    "id": "67bb934b",
    "metadata": {},
    "outputs": [
@@ -657,8 +343,8 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
-   "id": "e4c66f15",
+   "execution_count": 65,
+   "id": "3d7ef5a7",
    "metadata": {},
    "outputs": [
     {
@@ -675,7 +361,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 66,
    "id": "b6f77ac6",
    "metadata": {},
    "outputs": [
@@ -703,7 +389,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 67,
    "id": "246c2a58",
    "metadata": {},
    "outputs": [
@@ -723,7 +409,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 68,
    "id": "5a72ce30",
    "metadata": {},
    "outputs": [
@@ -741,7 +427,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": 69,
    "id": "59514dcd",
    "metadata": {},
    "outputs": [
@@ -761,7 +447,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 70,
    "id": "f3c19364",
    "metadata": {},
    "outputs": [
@@ -779,62 +465,1176 @@
     "-1234567890123456789012345678901234567890 to_bigint"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 71,
+   "id": "00daba0b",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "clear"
+   ]
+  },
   {
    "cell_type": "markdown",
-   "id": "4dbd0f30",
+   "id": "8157b5e7",
    "metadata": {},
    "source": [
-    "## Addition of Like Signs\n",
+    "## Addition of Like Signs `add-digits`\n",
+    "\n",
+    "Let's figure out how to add two lists of digits (we will assume that the signs are the same.)  We need to put an inital `false` value for a carry flag, and then there's a `genrec`.\n",
+    "\n",
+    "    initial-carry ≡ false rollup\n",
+    "      add-digits' ≡ [P] [THEN] [R0] [R1] genrec\n",
+    "      \n",
+    "       add-digits ≡ initial-carry add-digits'"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "fc9b97e4",
+   "metadata": {},
+   "source": [
+    "### The predicate\n",
     "\n",
     "I think we're going to want a recursive function (duh!?) but it's not quite a standard *hylomorphism* for (at least) two reasons:\n",
     "\n",
     "- We're tearing down two lists simultaneously.\n",
     "- They might not be the same length.\n",
     "\n",
-    "The base case would be two empty lists.  In that case the result is determined by the `carry` bit,  (Should zero be represented by the empty list `[]`, by `[0]`, or by both?) zero or one.\n",
-    "\n"
+    "There are two base cases: two empty lists or one empty list, the recursive branch is taken only if both lists at non-empty.\n",
+    "\n",
+    "    bool [a ...] [b ...] P\n",
+    "\n",
+    "The first thing to do is convert them to Booleans:"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
-   "id": "dd25bb96",
+   "execution_count": 72,
+   "id": "77eea97f",
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "false"
+      "[[true true] [true false] [false true] [false false]]"
      ]
     }
    ],
    "source": [
     "clear\n",
-    "\n",
-    "[] bool"
+    "[\n",
+    "[[a] [b]]\n",
+    "[[a] []]\n",
+    "[[] [b]]\n",
+    "[[] []]\n",
+    "]\n",
+    "[[[bool] ii] infra] \n",
+    "map"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
-   "id": "c9bdd641",
+   "execution_count": 73,
+   "id": "b3d917b2",
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "true"
+      "[[false] [true] [true] [true]]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "[\n",
+    "[[a] [b]]\n",
+    "[[a] []]\n",
+    "[[] [b]]\n",
+    "[[] []]\n",
+    "]\n",
+    "[[[bool] ii & not] infra] \n",
+    "map"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "c37e6dc8",
+   "metadata": {},
+   "source": [
+    "    P == [bool] ii & not"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "2f69bbd1",
+   "metadata": {},
+   "source": [
+    "### The base cases\n",
+    "We have to decide between three cases, but because addition we can lump together the first two cases:\n",
+    "\n",
+    "    bool [] [b ...] THEN\n",
+    "    bool [a ...] [] THEN\n",
+    "    bool [] [] THEN\n",
+    "\n",
+    "    THEN ≡ [P'] [THEN'] [ELSE] ifte"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 74,
+   "id": "4a36d545",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[[true] [true] [false]]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "[\n",
+    "[[a] []]\n",
+    "[[] [b]]\n",
+    "[[] []]\n",
+    "]\n",
+    "[[[bool] ii |] infra] \n",
+    "map"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "518f5c0d",
+   "metadata": {},
+   "source": [
+    "    P' ≡ [bool] ii |\n",
+    "\n",
+    "So `THEN'` deals with one number (list of digits) being longer than the other, while the `ELSE` branch deals with the case of both lists being empty."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "87db88e8",
+   "metadata": {},
+   "source": [
+    "#### One list empty\n",
+    "In the cases where one of the two lists (but not both) is empty:\n",
+    "\n",
+    "    carry [a ...] [] THEN'\n",
+    "    carry [] [b ...] THEN'\n",
+    "\n",
+    "We first get rid of the empty list:\n",
+    "\n",
+    "    ditch-empty-list ≡ [bool] [popd] [pop] ifte"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 75,
+   "id": "3af0bfc7",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "clear\n",
+    "[ditch-empty-list [bool] [popd] [pop] ifte] inscribe"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 76,
+   "id": "85030079",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[1]"
+     ]
+    }
+   ],
+   "source": [
+    "[1][] ditch-empty-list"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 77,
+   "id": "e4aafcaa",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[1]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "[][1] ditch-empty-list"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "76a60ef3",
+   "metadata": {},
+   "source": [
+    "    THEN' ≡ ditch-empty-list THEN''\n",
+    "\n",
+    "Now we have:\n",
+    "\n",
+    "    carry [n ...] THEN''\n",
+    "\n",
+    "This is `add-carry-to-digits` that kicked my ass earlier today.  Like I mentioned above, I think it was because I put it in the recursive branch!  D'oh!"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "b84cccef",
+   "metadata": {},
+   "source": [
+    "#### But first  `add-with-carry`\n",
+    "We will want some function `F` that accepts a bool and two ints and leaves behind a new int and a new Boolean carry flag:\n",
+    "\n",
+    "            carry0 a b F\n",
+    "    --------------------------\n",
+    "         (a+b+carry0) carry\n",
+    "\n",
+    "(I find it interesting that this function accepts the carry from below the int args but returns it above the result.  Hmm...)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 78,
+   "id": "3333e900",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0 1"
      ]
     }
    ],
    "source": [
     "clear\n",
     "\n",
-    "[] [] [bool not] ii &"
+    "[bool_to_int [0] [1] branch] inscribe\n",
+    "\n",
+    "false bool_to_int\n",
+    "true bool_to_int"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 79,
+   "id": "22a7c867",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "3"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "false 1 2 [bool_to_int] dipd + +"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 80,
+   "id": "75713ea2",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "4"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "true 1 2 [bool_to_int] dipd + +"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "a9417aac",
+   "metadata": {},
+   "source": [
+    "So the first part of `F` is `[bool_to_int] dipd + +` to get the total, then we need to"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 81,
+   "id": "b4f1000f",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "4 false"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "4 base [mod] [>=] clop"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 82,
+   "id": "ffbdf325",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "100 true"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "base 100 +\n",
+    "\n",
+    "base [mod] [>=] clop"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "f09689c3",
+   "metadata": {},
+   "source": [
+    "Put it all together and we have:\n",
+    "\n",
+    "    _add-with-carry0 ≡ [bool_to_int] dipd + +\n",
+    "    _add-with-carry1 ≡ base [mod] [>=] clop\n",
+    "\n",
+    "    add-with-carry ≡ _add-with-carry0 _add-with-carry1\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 83,
+   "id": "b8161efb",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "clear\n",
+    "[_add-with-carry0 [bool_to_int] dipd + +] inscribe\n",
+    "[_add-with-carry1 base [mod] [>=] clop] inscribe\n",
+    "[add-with-carry _add-with-carry0 _add-with-carry1] inscribe"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 84,
+   "id": "0f082af7",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "100 true"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "false base 100 add-with-carry"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 85,
+   "id": "a0d656bf",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "101 true"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "true base 100 add-with-carry"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 86,
+   "id": "fb7065be",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "102 false"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "false 2 100 add-with-carry"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 87,
+   "id": "9b91363f",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "103 false"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "true 2 100 add-with-carry"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 89,
+   "id": "5596f574",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "clear"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "861e6896",
+   "metadata": {},
+   "source": [
+    "### Now back to `add-carry-to-digits`\n",
+    "\n",
+    "This should be a very simple recursive function.\n",
+    "\n",
+    "    add-carry-to-digits ≡ [_actd_P] [_actd_THEN] [_actd_R0] [_actd_R1] genrec\n",
+    "\n",
+    "    carry [n ...] add-carry-to-digits\n",
+    "    carry [n ...] [_actd_P] [_actd_THEN] [_actd_R0] [_actd_R1] genrec\n",
+    "\n",
+    "The predicate is the carry flag itself inverted, but when we recur we need to check if the list is non-empty because it will eventually be empty or the carry flag will be false:\n",
+    "\n",
+    "    _actd_P ≡ pop not\n",
+    "\n",
+    "The base case simply discards the carry flag:\n",
+    "\n",
+    "    _actd_THEN ≡ popd"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "26ba75fb",
+   "metadata": {},
+   "source": [
+    "That leaves the recursive branch:\n",
+    "\n",
+    "    true [n ...] R0 [add-carry-to-digits] R1\n",
+    "\n",
+    "-or-\n",
+    "\n",
+    "    true [] R0 [add-carry-to-digits] R1"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "4d66332b",
+   "metadata": {},
+   "source": [
+    "We know that the Boolean value is `true`.  We also know that the list will be non-empty, but only on the first iteration of the `genrec`.  It may be that the list is empty on a later iteration.\n",
+    "\n",
+    "The `R0` function should check the list.\n",
+    "\n",
+    "    _actd_R0 ≡ [bool] [_actd_R0.then] [_actd_R0.else] ifte"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "4ed0fd33",
+   "metadata": {},
+   "source": [
+    "If it's empty...\n",
+    "\n",
+    "       true [] R0.else [add-carry-to-digits] R1\n",
+    "    ----------------------------------------------\n",
+    "           false [1] [add-carry-to-digits] R1\n",
+    "\n",
+    "    R0.else ≡ 1 swons popd false swap"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "e82f8749",
+   "metadata": {},
+   "source": [
+    "If it's not empty...\n",
+    "\n",
+    "       true [a ...] R0.then [add-carry-to-digits] R1\n",
+    "    -------------------------------------------------------------\n",
+    "       true 0 a add-with-carry [...1] [add-carry-to-digits] R1\n",
+    "    -------------------------------------------------------------\n",
+    "       (a+1) carry [...1] [add-carry-to-digits] R1"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "07f1bc97",
+   "metadata": {},
+   "source": [
+    "Ah ha!?  How to get that `(a+1)` back into the list!?\n",
+    "\n",
+    "If it's empty...\n",
+    "\n",
+    "       true [] R0.else [add-carry-to-digits] R1\n",
+    "    ------------------------------------------------\n",
+    "          1 false [] [add-carry-to-digits] i cons\n",
+    "\n",
+    "and\n",
+    "\n",
+    "       true [a ...] R0.then [add-carry-to-digits] i cons\n",
+    "    -------------------------------------------------------------\n",
+    "       true 0 a add-with-carry [...1] [add-carry-to-digits] i cons\n",
+    "    -------------------------------------------------------------\n",
+    "       (a+1) carry [...1] [add-carry-to-digits] i cons"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "9bfc7127",
+   "metadata": {},
+   "source": [
+    "There we go.\n",
+    "\n",
+    "    _actd_R0.else ≡ popd 1 false rolldown\n",
+    "\n",
+    "    _actd_R0.then ≡ 0 swap uncons [add-with-carry] dip\n",
+    "\n",
+    "    _actd_R1 ≡ i cons"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 90,
+   "id": "6bd105a9",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "[add-carry-to-digits [_actd_P] [_actd_THEN] [_actd_R0] [_actd_R1] genrec] inscribe\n",
+    "[_actd_P pop not] inscribe\n",
+    "[_actd_THEN popd] inscribe\n",
+    "[_actd_R0 [bool] [_actd_R0.then] [_actd_R0.else] ifte] inscribe\n",
+    "[_actd_R0.else popd 1 false rolldown] inscribe\n",
+    "[_actd_R0.then 0 swap uncons [add-with-carry] dip] inscribe\n",
+    "[_actd_R1 i cons] inscribe"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 91,
+   "id": "39244b26",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[3 2 1]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "false [3 2 1] add-carry-to-digits"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 92,
+   "id": "0a921fd7",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[1]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "true [] add-carry-to-digits"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 93,
+   "id": "94359309",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[4 2 1]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "true [3 2 1] add-carry-to-digits"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 94,
+   "id": "d5d4de95",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "true [2147483647 2 1]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "true base -- [2 1] cons "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 95,
+   "id": "a34b4771",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[0 3 1]"
+     ]
+    }
+   ],
+   "source": [
+    "add-carry-to-digits"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "181cdfd4",
+   "metadata": {},
+   "source": [
+    "So that handles the cases where one of the two lists (but not both) is empty.\n",
+    "\n",
+    "#### Both lists empty\n",
+    "If both lists are empty we discard one list and check the carry to determine our result as decribed above:\n",
+    "\n",
+    "    ELSE ≡ pop swap [] [1 swons] branch"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 96,
+   "id": "5e5ddf74",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[1]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "true [] [] pop swap [] [1 swons] branch"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 97,
+   "id": "c57d1fb2",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "false [] [] pop swap [] [1 swons] branch"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 98,
+   "id": "59b1338c",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "clear"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "c4454f63",
+   "metadata": {},
+   "source": [
+    "The story so far...\n",
+    "\n",
+    "    add-digits ≡ initial-carry add-digits'\n",
+    "    \n",
+    "    add-digits' ≡ [P] [THEN] [R0] [R1] genrec\n",
+    "\n",
+    "    initial-carry ≡ false rollup\n",
+    "\n",
+    "    P ≡ [bool] ii & not\n",
+    "\n",
+    "    THEN ≡ [P'] [THEN'] [ELSE] ifte\n",
+    "\n",
+    "    P' ≡ [bool] ii |\n",
+    "\n",
+    "    THEN' ≡ ditch-empty-list add-carry-to-digits\n",
+    "\n",
+    "    ELSE ≡ pop swap [] [1 swons] branch\n",
+    "\n",
+    "We just need to knock out those recursive functions `R0` and `R1` and we're done."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "54632eea",
+   "metadata": {},
+   "source": [
+    "### And recur...\n",
+    "\n",
+    "    bool [a ...] [b ...] R0 [add-digits'] R1"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "995bd8d3",
+   "metadata": {},
+   "source": [
+    "First we will want to `uncons` the digits"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 99,
+   "id": "02c19af8",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "false 1 4 [2 3] [5 6]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "false [1 2 3] [4 5 6] [uncons] ii swapd"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "9557420b",
+   "metadata": {},
+   "source": [
+    "#### `uncons-two`\n",
+    "We could call this `uncons-two`:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 100,
+   "id": "5d671aa4",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "1 4 [2 3] [5 6]"
+     ]
+    }
+   ],
+   "source": [
+    "clear\n",
+    "\n",
+    "[uncons-two [uncons] ii swapd] inscribe\n",
+    "\n",
+    "[1 2 3] [4 5 6] uncons-two"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 102,
+   "id": "80eab7d7",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "clear"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "a47c67cf",
+   "metadata": {},
+   "source": [
+    "    bool a b [...] [...] R0' [add-digits'] R1\n",
+    "\n",
+    "It's at this point that we'll want to employ the `add-with-carry` function:\n",
+    "\n",
+    "    bool a b [...] [...] [add-with-carry] dipd R0'' [add-digits'] R1\n",
+    "\n",
+    "    bool a b add-with-carry [...] [...] R0'' [add-digits'] R1\n",
+    "\n",
+    "    (a+b) bool [...] [...] R0'' [add-digits'] R1\n",
+    "\n",
+    "If we postulate a `cons` in our `R1` function...\n",
+    "\n",
+    "    (a+b) bool [...] [...] R0'' [add-digits'] i cons\n",
+    "\n",
+    "Then it seems like we're done?  `R0''` is nothing?\n",
+    "\n",
+    "    R0 ≡ uncons-two [add-with-carry] dipd\n",
+    "    \n",
+    "    R1 ≡ i cons\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 103,
+   "id": "a16c95cf",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "[add-digits initial-carry add-digits'] inscribe\n",
+    "[add-digits' [P] [THEN] [R0] [R1] genrec] inscribe\n",
+    "[initial-carry false rollup] inscribe\n",
+    "[P [bool] ii & not] inscribe\n",
+    "[THEN [P'] [THEN'] [ELSE] ifte] inscribe\n",
+    "[P' [bool] ii |] inscribe\n",
+    "[THEN' ditch-empty-list add-carry-to-digits] inscribe\n",
+    "[ELSE pop swap [] [1 swons] branch] inscribe\n",
+    "[R0 uncons-two [add-with-carry] dipd] inscribe\n",
+    "[R1 i cons] inscribe\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 104,
+   "id": "66176a8f",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[3 2 1] [1 1 1]"
+     ]
+    }
+   ],
+   "source": [
+    "[3 2 1] [1 1 1]"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 105,
+   "id": "e0272194",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[4 3 2]"
+     ]
+    }
+   ],
+   "source": [
+    "add-digits"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 106,
+   "id": "bec3b32d",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[4 3 2] [2147483647]"
+     ]
+    }
+   ],
+   "source": [
+    "base -- unit"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 107,
+   "id": "6d8b0054",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[3 4 2]"
+     ]
+    }
+   ],
+   "source": [
+    "add-digits"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 108,
+   "id": "c842f875",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[3 4 2] [2147483647 2147483647 2147483647]"
+     ]
+    }
+   ],
+   "source": [
+    "base -- dup dup unit ccons"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 109,
+   "id": "80a240b0",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[2 4 2 1]"
+     ]
+    }
+   ],
+   "source": [
+    "add-digits"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "558e0a6d",
+   "metadata": {},
+   "source": [
+    "243 + 999 = "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 110,
+   "id": "31aa6611",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "1242"
+     ]
+    }
+   ],
+   "source": [
+    "clear 243 999 +"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "db2de9c5",
+   "metadata": {},
+   "source": [
+    "Bitchin'"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "a46d9942",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "4fe39366",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "ef9db281",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "834ee60c",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "20a2809e",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "b74e8780",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "b2765992",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "c96c51a5",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
   {
    "cell_type": "markdown",
    "id": "50665e75",
@@ -942,87 +1742,6 @@
     "[1][1]_add_p"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "id": "abe20e0b",
-   "metadata": {},
-   "source": [
-    "### Base Case\n",
-    "In the base case we discard one list and check the carry to determine our result as decribed above:"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 127,
-   "id": "5e5ddf74",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[1]"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "true [] [] pop swap [] [1 swons] branch"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 128,
-   "id": "c57d1fb2",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[]"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "false [] [] pop swap [] [1 swons] branch"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 129,
-   "id": "59b1338c",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": []
-    }
-   ],
-   "source": [
-    "clear"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 31,
-   "id": "ed38fdb1",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": []
-    }
-   ],
-   "source": [
-    "[_add_then pop swap [] [1 swons] branch] inscribe"
-   ]
-  },
   {
    "cell_type": "markdown",
    "id": "978b5cac",
@@ -1160,386 +1879,6 @@
     "[_add_rec_pred [bool] ii &] inscribe"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "id": "2adf3f59",
-   "metadata": {},
-   "source": [
-    "#### `true` branch\n",
-    "Let's square away the `true` branch first.\n",
-    "\n",
-    "    carry [a ...] [b ...] ... [add_digits] ...\n",
-    "\n",
-    "First we will want to `uncons` the digits"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 95,
-   "id": "1e53236f",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "false 1 4 [2 3] [5 6]"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "false [1 2 3] [4 5 6] [uncons] ii swapd"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "id": "8d66b26b",
-   "metadata": {},
-   "source": [
-    "#### add-with-carry\n",
-    "So now we want some function `F` to `dipd` below the list tails that accepts a bool and two ints and leaves behind a new int and a new Boolean carry flag:\n",
-    "\n",
-    "            carry0 a b F\n",
-    "    --------------------------\n",
-    "         (a+b+carry0) carry\n",
-    "\n",
-    "(I find it interesting that this function accepts the carry from below the int args but returns it above the result.  Hmm...)"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 96,
-   "id": "2f70ca25",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "0 1"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "[bool_to_int [0] [1] branch] inscribe\n",
-    "\n",
-    "false bool_to_int\n",
-    "true bool_to_int"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 97,
-   "id": "c19916c5",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "3"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "false 1 2 [bool_to_int] dipd + +"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 98,
-   "id": "ead4cc5e",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "4"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "true 1 2 [bool_to_int] dipd + +"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "id": "ddb201ca",
-   "metadata": {},
-   "source": [
-    "So the first part of `F` is `[bool_to_int] dipd + +` to get the total, then we need to"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 99,
-   "id": "129997e0",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "4"
-     ]
-    }
-   ],
-   "source": [
-    "base mod"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 100,
-   "id": "22209a15",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "false"
-     ]
-    }
-   ],
-   "source": [
-    "base >="
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 101,
-   "id": "57649cf3",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "4 false"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "4 base [mod] [>=] clop"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 102,
-   "id": "3c2e42be",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "100 true"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "base 100 +\n",
-    "\n",
-    "base [mod] [>=] clop"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "id": "893a39c4",
-   "metadata": {},
-   "source": [
-    "\n",
-    "    F == [bool_to_int] dipd + + base [mod] [>=] clop\n"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 103,
-   "id": "257d757c",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": []
-    }
-   ],
-   "source": [
-    "clear\n",
-    "[_add-with-carry0 [bool_to_int] dipd + +] inscribe\n",
-    "[_add-with-carry1 base [mod] [>=] clop] inscribe\n",
-    "[add-with-carry _add-with-carry0 _add-with-carry1] inscribe"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 104,
-   "id": "1d50a1c6",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "100 true"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "false base 100 add-with-carry"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 105,
-   "id": "b93ae376",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "101 true"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "true base 100 add-with-carry"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 106,
-   "id": "4f86c2c7",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "102 false"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "false 2 100 add-with-carry"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 107,
-   "id": "68a8a9c2",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "103 false"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "true 2 100 add-with-carry"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "id": "e9a512f0",
-   "metadata": {},
-   "source": [
-    "Going back to our `true` branch we have:"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 108,
-   "id": "74873f5b",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "false 1 4 [2 3] [5 6]"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "false [1 2 3] [4 5 6] [uncons] ii swapd"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "id": "5520db54",
-   "metadata": {},
-   "source": [
-    "#### `uncons-two`\n",
-    "We could call this `uncons-two`:"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 116,
-   "id": "e7176ea9",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "1 4 [2 3] [5 6]"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "\n",
-    "[uncons-two [uncons] ii swapd] inscribe\n",
-    "\n",
-    "[1 2 3] [4 5 6] uncons-two"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 117,
-   "id": "64b575f7",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": []
-    }
-   ],
-   "source": [
-    "clear"
-   ]
-  },
   {
    "cell_type": "markdown",
    "id": "9445eb3c",
@@ -1651,75 +1990,6 @@
     "clear"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "id": "85a49679",
-   "metadata": {},
-   "source": [
-    "#### `false` branch\n",
-    "And now we deal with the cases where one of the two lists (but not both) is empty:\n",
-    "\n",
-    "    carry [a ...] [] ELSE\n",
-    "    carry [] [b ...] ELSE\n",
-    "\n",
-    "We get rid of the empty list:\n",
-    "\n",
-    "[bool] [popd] [pop] ifte"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 113,
-   "id": "affd02fb",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": []
-    }
-   ],
-   "source": [
-    "[ditch-empty-list [bool] [popd] [pop] ifte] inscribe"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 114,
-   "id": "5cc19cea",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[1]"
-     ]
-    }
-   ],
-   "source": [
-    "[1][] ditch-empty-list"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 115,
-   "id": "12d72692",
-   "metadata": {},
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[1]"
-     ]
-    }
-   ],
-   "source": [
-    "clear\n",
-    "[][1] ditch-empty-list"
-   ]
-  },
   {
    "cell_type": "markdown",
    "id": "aa76c2fc",