funkykb/fsharp/discriminated-unions/grouping-with-discriminated-unions.ipynb

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    "# Grouping with Discriminated Unions\n",
    "\n",
    "The C# developer has desired to list elements of different types without boxing them in `object`. What appears to be a foundational use case of Discriminated Unions in F# is to accomplish this. Let’s look at the alphabet:"
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    "#!fsharp\n",
    "\n",
    "let alphabet = \"abcdefghijklmnopqrstuvwxyz\"\n",
    "\n",
    "26/8"
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   "source": [
    "We can chunk the alphabet into four groups:"
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       "<table><thead><tr><th><i>index</i></th><th>value</th></tr></thead><tbody><tr><td>0</td><td><div class=\"dni-plaintext\"><pre>[ a, b, c, d, e, f, g, h ]</pre></div></td></tr><tr><td>1</td><td><div class=\"dni-plaintext\"><pre>[ i, j, k, l, m, n, o, p ]</pre></div></td></tr><tr><td>2</td><td><div class=\"dni-plaintext\"><pre>[ q, r, s, t, u, v, w, x ]</pre></div></td></tr><tr><td>3</td><td><div class=\"dni-plaintext\"><pre>[ y, z ]</pre></div></td></tr></tbody></table><style>\r\n",
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    "#!fsharp\n",
    "\n",
    "alphabet.ToCharArray() |> Array.chunkBySize 8"
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    "We can use this chunk data to define a discriminated union of `AlphaGroup`:"
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    "#!fsharp\n",
    "\n",
    "type AlphaGroup =\n",
    "    | AthroughH of string\n",
    "    | IthroughP of string\n",
    "    | QthroughX of string\n",
    "    | YthroughZ of string"
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   "source": [
    "We can now list _all_ of these union types in a `List<AlphaGroup>` (which is totally awesome):"
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    "#!fsharp\n",
    "\n",
    "let data: AlphaGroup list =\n",
    "    [\n",
    "        AthroughH \"cat\"\n",
    "        AthroughH \"egg\"\n",
    "        IthroughP \"jack\"\n",
    "        YthroughZ \"yam\"\n",
    "        YthroughZ \"year\"\n",
    "        AthroughH \"ear\"\n",
    "        AthroughH \"eye\"\n",
    "        QthroughX \"ribbon\"\n",
    "        IthroughP \"jam\"\n",
    "        YthroughZ \"zoo\"\n",
    "    ]"
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   "source": [
    "We can now use the type system to group our `data` (with `GetType().Name`):"
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       "<table><thead><tr><th><i>index</i></th><th>Item1</th><th>Item2</th></tr></thead><tbody><tr><td>0</td><td>AthroughH</td><td><div class=\"dni-plaintext\"><pre>FSharpList&lt;AlphaGroup&gt;\n",
       "      - Item: cat\n",
       "      - Item: egg\n",
       "      - Item: ear\n",
       "      - Item: eye</pre></div></td></tr><tr><td>1</td><td>IthroughP</td><td><div class=\"dni-plaintext\"><pre>FSharpList&lt;AlphaGroup&gt;\n",
       "      - Item: jack\n",
       "      - Item: jam</pre></div></td></tr><tr><td>2</td><td>QthroughX</td><td><div class=\"dni-plaintext\"><pre>FSharpList&lt;AlphaGroup&gt;\n",
       "      - Item: ribbon</pre></div></td></tr><tr><td>3</td><td>YthroughZ</td><td><div class=\"dni-plaintext\"><pre>FSharpList&lt;AlphaGroup&gt;\n",
       "      - Item: yam\n",
       "      - Item: year\n",
       "      - Item: zoo</pre></div></td></tr></tbody></table><style>\r\n",
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    "data |> List.groupBy (fun item -> item.GetType().Name) |> List.sortBy (fun (typeName, _) -> typeName)"
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   "source": [
    "@[BryanWilhite](https://twitter.com/BryanWilhite)"
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