Cleanup and refactoring.

Bug when subtracting identical numbers.  It gives

    [false 0]

When it should be

    [false]

or better yet

    [true]

eh?

docs/notebooks/BigInts.ipynb

@@ -5080,7 +5080,7 @@
   {
    "cell_type": "code",
    "execution_count": 211,
-   "id": "3d29ed60",
+   "id": "90abab0f",
    "metadata": {},
    "outputs": [
     {
@@ -5095,7 +5095,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "cb2fe4bb",
+   "id": "64b84d78",
    "metadata": {},
    "source": [
     "#### `neg-bigint`"
@@ -5104,7 +5104,7 @@
   {
    "cell_type": "code",
    "execution_count": 212,
-   "id": "47d10c16",
+   "id": "391d87fe",
    "metadata": {},
    "outputs": [
     {
@@ -5120,7 +5120,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "781a1ed2",
+   "id": "a7cce3f2",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -5130,7 +5130,7 @@
   {
    "cell_type": "code",
    "execution_count": 213,
-   "id": "e2bf4564",
+   "id": "edb25ebd",
    "metadata": {},
    "outputs": [
     {
@@ -5148,7 +5148,7 @@
   {
    "cell_type": "code",
    "execution_count": 214,
-   "id": "9b4c3ea7",
+   "id": "06e2f309",
    "metadata": {},
    "outputs": [
     {
@@ -5165,59 +5165,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "id": "7c4edc9a",
+   "execution_count": 215,
+   "id": "dd47bdae",
    "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "8d467543",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "5722d274",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "d08a5ea1",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "4e18e84a",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "b72d58e6",
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "id": "f134ab23",
-   "metadata": {},
-   "outputs": [],
-   "source": []
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": []
+    }
+   ],
+   "source": [
+    "clear\n",
+    "[sub-bigints [same-sign] [sub-like-bigints] [neg-bigint add-like-bigints] ifte] inscribe\n",
+    "[add-bigints [same-sign] [add-like-bigints] [neg-bigint sub-like-bigints] ifte] inscribe"
+   ]
   },
   {
    "cell_type": "markdown",