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<pre class="alectryon-io"><!-- Generator: Alectryon v1.0 --><span class="coq-wsp"><span class="highlight"><span class="c">(* </span>
<span class="c"> * Vericert: Verified high-level synthesis.</span>
<span class="c"> * Copyright (C) 2019-2020 Yann Herklotz &lt;yann@yannherklotz.com&gt;</span>
<span class="c"> *</span>
<span class="c"> * This program is free software: you can redistribute it and/or modify</span>
<span class="c"> * it under the terms of the GNU General Public License as published by</span>
<span class="c"> * the Free Software Foundation, either version 3 of the License, or</span>
<span class="c"> * (at your option) any later version.</span>
<span class="c"> *</span>
<span class="c"> * This program is distributed in the hope that it will be useful,</span>
<span class="c"> * but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<span class="c"> * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the</span>
<span class="c"> * GNU General Public License for more details.</span>
<span class="c"> *</span>
<span class="c"> * You should have received a copy of the GNU General Public License</span>
<span class="c"> * along with this program.  If not, see &lt;https://www.gnu.org/licenses/&gt;.</span>
<span class="c"> *)</span>

</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">From</span> Coq <span class="kn">Require Import</span>
    Strings.String
    Bool.Bool
    Arith.Arith
    ZArith.ZArith.</span></span><span class="coq-wsp">
</span></span><span class="coq-wsp"><span class="highlight">
</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">Local Open Scope</span> string.</span></span><span class="coq-wsp">
</span></span><span class="coq-wsp"><span class="highlight">
</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">Class</span> <span class="nf">Show</span> <span class="nv">A</span> : <span class="kt">Type</span> :=
  {
  show : A -&gt; string
  }.</span></span><span class="coq-wsp">
</span></span><span class="coq-wsp"><span class="highlight">
</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">Instance</span> <span class="nf">showBool</span> : <span class="kn">Show</span> bool :=
  {
  show := <span class="kr">fun</span> <span class="nv">b</span>:bool =&gt; <span class="kr">if</span> b <span class="kr">then</span> <span class="s2">&quot;true&quot;</span> <span class="kr">else</span> <span class="s2">&quot;false&quot;</span>
  }.</span></span><span class="coq-wsp">
</span></span><span class="coq-wsp"><span class="highlight">
</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">Fixpoint</span> <span class="nf">string_of_nat_aux</span> (<span class="nv">time</span> <span class="nv">n</span> : nat) (<span class="nv">acc</span> : string) : string :=
  <span class="kr">let</span> <span class="nv">d</span> := <span class="kr">match</span> n mod <span class="mi">10</span> <span class="kr">with</span>
           | <span class="mi">0</span> =&gt; <span class="s2">&quot;0&quot;</span> | <span class="mi">1</span> =&gt; <span class="s2">&quot;1&quot;</span> | <span class="mi">2</span> =&gt; <span class="s2">&quot;2&quot;</span> | <span class="mi">3</span> =&gt; <span class="s2">&quot;3&quot;</span> | <span class="mi">4</span> =&gt; <span class="s2">&quot;4&quot;</span> | <span class="mi">5</span> =&gt; <span class="s2">&quot;5&quot;</span>
           | <span class="mi">6</span> =&gt; <span class="s2">&quot;6&quot;</span> | <span class="mi">7</span> =&gt; <span class="s2">&quot;7&quot;</span> | <span class="mi">8</span> =&gt; <span class="s2">&quot;8&quot;</span> | _ =&gt; <span class="s2">&quot;9&quot;</span>
           <span class="kr">end</span> <span class="kr">in</span>
  <span class="kr">let</span> <span class="nv">acc&#39;</span> := d ++ acc <span class="kr">in</span>
  <span class="kr">match</span> <span class="kp">time</span> <span class="kr">with</span>
  | <span class="mi">0</span> =&gt; acc&#39;
  | S time&#39; =&gt;
    <span class="kr">match</span> n / <span class="mi">10</span> <span class="kr">with</span>
    | <span class="mi">0</span> =&gt; acc&#39;
    | n&#39; =&gt; string_of_nat_aux time&#39; n&#39; acc&#39;
    <span class="kr">end</span>
  <span class="kr">end</span>.</span></span><span class="coq-wsp">
</span></span><span class="coq-wsp"><span class="highlight">
</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">Definition</span> <span class="nf">string_of_nat</span> (<span class="nv">n</span> : nat) : string :=
  string_of_nat_aux n n <span class="s2">&quot;&quot;</span>.</span></span><span class="coq-wsp">
</span></span><span class="coq-wsp"><span class="highlight">
</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">Instance</span> <span class="nf">showNat</span> : <span class="kn">Show</span> nat :=
  {
  show := string_of_nat
  }.</span></span><span class="coq-wsp">
</span></span><span class="coq-wsp"><span class="highlight">
</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">Instance</span> <span class="nf">showZ</span> : <span class="kn">Show</span> Z :=
  {
  show a := show (Z.to_nat a)
  }.</span></span><span class="coq-wsp">
</span></span><span class="coq-wsp"><span class="highlight">
</span></span><span class="coq-sentence"><span class="coq-input"><span class="highlight"><span class="kn">Instance</span> <span class="nf">showPositive</span> : <span class="kn">Show</span> positive :=
  {
  show a := show (Zpos a)
  }.</span></span></span></pre>
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