|
10 | 10 | <email>usefulalgorithm@gmail.com</email> |
11 | 11 |
|
12 | 12 | </author> |
13 | | - <updated>2025-04-23T00:00:00Z</updated> |
| 13 | + <updated>2025-04-27T00:00:00Z</updated> |
14 | 14 | <entry> |
| 15 | + <title>Civilistjävel - Följd</title> |
| 16 | + <link href="http://usefulalgorithm.github.io/posts/2025-04-27-fljd-civilistjvel.html" /> |
| 17 | + <id>http://usefulalgorithm.github.io/posts/2025-04-27-fljd-civilistjvel.html</id> |
| 18 | + <published>2025-04-27T00:00:00Z</published> |
| 19 | + <updated>2025-04-27T00:00:00Z</updated> |
| 20 | + <summary type="html"><![CDATA[<article> |
| 21 | + <section class="header"> |
| 22 | + Posted on April 27, 2025 |
| 23 | + |
| 24 | + <br> |
| 25 | + |
| 26 | + Tags: <a title="All pages tagged '2025'." href="/tags/2025.html" rel="tag">2025</a>, <a title="All pages tagged 'music'." href="/tags/music.html" rel="tag">music</a>, <a title="All pages tagged 'ambient， dub techno'." href="/tags/ambient%EF%BC%8C%20dub%20techno.html" rel="tag">ambient， dub techno</a> |
| 27 | + |
| 28 | + </section> |
| 29 | + <section> |
| 30 | + <p><img src="https://f4.bcbits.com/img/a2320697940_10.jpg" /></p> |
| 31 | +<p>去年他發的 <em>Brödföda</em> 我很喜歡，這張則是它的續作，風格上更極簡一點。也有更多 dub techno 歌，像十分鐘的 “XVI” 就很讚。</p> |
| 32 | +<hr /> |
| 33 | +<p>Fav tracks: XIV, XVI, XVII |
| 34 | +Score: 8.1/10</p> |
| 35 | +<p>Release date: 2025-02-14</p> |
| 36 | +<p>Labels: Rubadub</p> |
| 37 | + </section> |
| 38 | +</article> |
| 39 | +]]></summary> |
| 40 | +</entry> |
| 41 | +<entry> |
15 | 42 | <title>Barker - Stochastic Drift</title> |
16 | 43 | <link href="http://usefulalgorithm.github.io/posts/2025-04-23-stochasticdrift-barker.html" /> |
17 | 44 | <id>http://usefulalgorithm.github.io/posts/2025-04-23-stochasticdrift-barker.html</id> |
|
255 | 282 | </article> |
256 | 283 | ]]></summary> |
257 | 284 | </entry> |
258 | | -<entry> |
259 | | - <title>Using Haskell to generate post template (or, using Haskell in inappropriate places)</title> |
260 | | - <link href="http://usefulalgorithm.github.io/posts/2025-03-25-pulling-album-info.html" /> |
261 | | - <id>http://usefulalgorithm.github.io/posts/2025-03-25-pulling-album-info.html</id> |
262 | | - <published>2025-03-25T00:00:00Z</published> |
263 | | - <updated>2025-03-25T00:00:00Z</updated> |
264 | | - <summary type="html"><![CDATA[<article> |
265 | | - <section class="header"> |
266 | | - Posted on March 25, 2025 |
267 | | - |
268 | | - <br> |
269 | | - |
270 | | - Tags: <a title="All pages tagged 'about this blog'." href="/tags/about%20this%20blog.html" rel="tag">about this blog</a>, <a title="All pages tagged 'haskell'." href="/tags/haskell.html" rel="tag">haskell</a> |
271 | | - |
272 | | - </section> |
273 | | - <section> |
274 | | - <p>我前陣子太閒，就想要自動地在我執行 Github workflow 的時候去觸發一個腳本，從一些網路上的資料庫抓我想要寫的專輯的相關資料。一般來說，做這種事情通常是直接用 Python 或是 Bash script + <code>jq</code> 之類的，又簡單又好懂，不過我天生喜歡瞎忙，想說既然都在用 Haskell 了，不如也來用 Haskell 寫這腳本。事實證明真的是比用 Python 麻煩很多…</p> |
275 | | -<h3 id="從哪裡抓專輯資料">從哪裡抓專輯資料？</h3> |
276 | | -<p>我本來以為可以從 Bandcamp 去拉，但我寫信去要 API key 時，得到的回覆是沒有公開 API 可以拿到某張專輯的資訊。網上有一些專案好像可以不用爬蟲不用 API key 去拿到專輯資訊，不過看起來有點醜，就覺得算了。最後決定直接從 <a href="https://www.discogs.com/developers">Discogs</a> 上面抓。做法是先用 <code>search</code> 找到某張專輯的 <a href="https://support.discogs.com/hc/en-us/articles/360005055493-Database-Guidelines-16-Master-Release">master release</a>，拿到 master release 的 id，再用這個 id 去查找專輯的發行日期、廠牌跟封面。如果這張專輯太冷門，根本沒有 master release 的話，那麼就直接挑第一個 release，用它的 id 去拿我要的資訊。</p> |
277 | | -<h3 id="用-haskell-解析-json-資料">用 Haskell 解析 JSON 資料</h3> |
278 | | -<p>處理 JSON 資料時，Haskell 通常用 <a href="https://hackage.haskell.org/package/aeson">aeson</a>。使用方式是先定義一個資料結構：</p> |
279 | | -<div class="sourceCode" id="cb1"><pre class="sourceCode haskell"><code class="sourceCode haskell"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="kw">data</span> <span class="dt">Release</span> <span class="ot">=</span> <span class="dt">Release</span> {</span> |
280 | | -<span id="cb1-2"><a href="#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="ot"> artists ::</span> [<span class="dt">String</span>],</span> |
281 | | -<span id="cb1-3"><a href="#cb1-3" aria-hidden="true" tabindex="-1"></a><span class="ot"> title ::</span> <span class="dt">String</span>,</span> |
282 | | -<span id="cb1-4"><a href="#cb1-4" aria-hidden="true" tabindex="-1"></a><span class="ot"> year ::</span> <span class="dt">Int</span>,</span> |
283 | | -<span id="cb1-5"><a href="#cb1-5" aria-hidden="true" tabindex="-1"></a><span class="ot"> released ::</span> <span class="dt">String</span>,</span> |
284 | | -<span id="cb1-6"><a href="#cb1-6" aria-hidden="true" tabindex="-1"></a><span class="ot"> imageUrl ::</span> <span class="dt">String</span>,</span> |
285 | | -<span id="cb1-7"><a href="#cb1-7" aria-hidden="true" tabindex="-1"></a><span class="ot"> labels ::</span> [<span class="dt">String</span>],</span> |
286 | | -<span id="cb1-8"><a href="#cb1-8" aria-hidden="true" tabindex="-1"></a><span class="ot"> uri ::</span> <span class="dt">String</span></span> |
287 | | -<span id="cb1-9"><a href="#cb1-9" aria-hidden="true" tabindex="-1"></a>} <span class="kw">deriving</span> (<span class="dt">Show</span>, <span class="dt">Eq</span>, <span class="dt">Generic</span>)</span></code></pre></div> |
288 | | -<p>接著實作 <code>ToJSON</code> 和 <code>FromJSON</code>。<code>ToJSON</code> 很簡單，直接把資料結構轉成 JSON 格式；<code>FromJSON</code> 就麻煩多了，得詳細定義如何把 JSON 轉成資料結構：</p> |
289 | | -<div class="sourceCode" id="cb2"><pre class="sourceCode haskell"><code class="sourceCode haskell"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="kw">instance</span> <span class="dt">ToJSON</span> <span class="dt">Release</span> <span class="co">-- 無腦轉</span></span> |
290 | | -<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a></span> |
291 | | -<span id="cb2-3"><a href="#cb2-3" aria-hidden="true" tabindex="-1"></a><span class="kw">instance</span> <span class="dt">FromJSON</span> <span class="dt">Release</span> <span class="kw">where</span></span> |
292 | | -<span id="cb2-4"><a href="#cb2-4" aria-hidden="true" tabindex="-1"></a> parseJSON (<span class="dt">Object</span> v) <span class="ot">=</span> <span class="kw">do</span></span> |
293 | | -<span id="cb2-5"><a href="#cb2-5" aria-hidden="true" tabindex="-1"></a> artists <span class="ot"><-</span> v <span class="op">.:</span> <span class="st">"artists"</span> <span class="op">>>=</span> <span class="fu">traverse</span> (<span class="op">.:</span> <span class="st">"name"</span>) <span class="co">-- "artists" 是個陣列，這裡的意思是取出陣列中每個元素的 "name"</span></span> |
294 | | -<span id="cb2-6"><a href="#cb2-6" aria-hidden="true" tabindex="-1"></a> title <span class="ot"><-</span> v <span class="op">.:</span> <span class="st">"title"</span> <span class="co">-- .: 表示從 v 中取出 "title" 的值</span></span> |
295 | | -<span id="cb2-7"><a href="#cb2-7" aria-hidden="true" tabindex="-1"></a> year <span class="ot"><-</span> v <span class="op">.:</span> <span class="st">"year"</span></span> |
296 | | -<span id="cb2-8"><a href="#cb2-8" aria-hidden="true" tabindex="-1"></a> released <span class="ot"><-</span> v <span class="op">.:</span> <span class="st">"released"</span></span> |
297 | | -<span id="cb2-9"><a href="#cb2-9" aria-hidden="true" tabindex="-1"></a> images <span class="ot"><-</span> v <span class="op">.:</span> <span class="st">"images"</span></span> |
298 | | -<span id="cb2-10"><a href="#cb2-10" aria-hidden="true" tabindex="-1"></a> imageUrl <span class="ot"><-</span> <span class="kw">case</span> images <span class="kw">of</span></span> |
299 | | -<span id="cb2-11"><a href="#cb2-11" aria-hidden="true" tabindex="-1"></a> (img<span class="op">:</span>_) <span class="ot">-></span> img <span class="op">.:</span> <span class="st">"resource_url"</span></span> |
300 | | -<span id="cb2-12"><a href="#cb2-12" aria-hidden="true" tabindex="-1"></a> [] <span class="ot">-></span> <span class="fu">fail</span> <span class="st">"No images found"</span></span> |
301 | | -<span id="cb2-13"><a href="#cb2-13" aria-hidden="true" tabindex="-1"></a> labels <span class="ot"><-</span> v <span class="op">.:</span> <span class="st">"labels"</span> <span class="op">>>=</span> <span class="fu">traverse</span> (<span class="op">.:</span> <span class="st">"name"</span>)</span> |
302 | | -<span id="cb2-14"><a href="#cb2-14" aria-hidden="true" tabindex="-1"></a> uri <span class="ot"><-</span> v <span class="op">.:</span> <span class="st">"uri"</span></span> |
303 | | -<span id="cb2-15"><a href="#cb2-15" aria-hidden="true" tabindex="-1"></a> <span class="fu">return</span> <span class="dt">Release</span> {</span> |
304 | | -<span id="cb2-16"><a href="#cb2-16" aria-hidden="true" tabindex="-1"></a> artists <span class="ot">=</span> artists,</span> |
305 | | -<span id="cb2-17"><a href="#cb2-17" aria-hidden="true" tabindex="-1"></a> title <span class="ot">=</span> title,</span> |
306 | | -<span id="cb2-18"><a href="#cb2-18" aria-hidden="true" tabindex="-1"></a> year <span class="ot">=</span> year,</span> |
307 | | -<span id="cb2-19"><a href="#cb2-19" aria-hidden="true" tabindex="-1"></a> released <span class="ot">=</span> released,</span> |
308 | | -<span id="cb2-20"><a href="#cb2-20" aria-hidden="true" tabindex="-1"></a> imageUrl <span class="ot">=</span> imageUrl,</span> |
309 | | -<span id="cb2-21"><a href="#cb2-21" aria-hidden="true" tabindex="-1"></a> labels <span class="ot">=</span> labels,</span> |
310 | | -<span id="cb2-22"><a href="#cb2-22" aria-hidden="true" tabindex="-1"></a> uri <span class="ot">=</span> uri</span> |
311 | | -<span id="cb2-23"><a href="#cb2-23" aria-hidden="true" tabindex="-1"></a> }</span></code></pre></div> |
312 | | -<p>可以看出來，如果資料結構很複雜，解析起來就得定義一堆結構來對應。用 Python 的話，這有點像寫一堆 Pydantic class，但每個 class 都得自己實作 <code>decode</code>。</p> |
313 | | -<p>另一個麻煩點是，當你只想取一個深層的值時，Haskell 就有點麻煩了。對比下面兩行程式碼：</p> |
314 | | -<div class="sourceCode" id="cb3"><pre class="sourceCode haskell"><code class="sourceCode haskell"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a>body <span class="op">^?</span> key <span class="st">"results"</span> <span class="op">.</span> nth <span class="dv">0</span> <span class="op">.</span> key (fromString queryKey) <span class="op">.</span> _Integer</span></code></pre></div> |
315 | | -<p>跟</p> |
316 | | -<div class="sourceCode" id="cb4"><pre class="sourceCode python"><code class="sourceCode python"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a><span class="bu">int</span>(body[<span class="st">"results"</span>][<span class="dv">0</span>][queryKey])</span></code></pre></div> |
317 | | -<p>可能我很淺？但我覺得 Python 的好讀多了。另外如果要在 Haskell 做這種操作，需要引入 <a href="https://hackage.haskell.org/package/lens-aeson">lens-aeson</a> 套件，原生是不支援的。</p> |
318 | | -<h3 id="套件管理">套件管理</h3> |
319 | | -<p>Haskell 的套件管理工具有 cabal 和 stack，感覺有點像 pip 和 poetry，但功能重疊得更多。</p> |
320 | | -<h3 id="在-github-workflow-裡執行-haskell-程式">在 Github workflow 裡執行 Haskell 程式</h3> |
321 | | -<p>如果每次在 workflow 裡面跑的時候都要重新 <code>stack build</code> （可以想像就是 <code>make build</code>）的話會花很多時間，實測下來大概需要二十分鐘左右。真的是太久了… 幸好有個專案就是在做 <a href="https://github.com/freckle/stack-action/tree/v5/">stack action</a>，快取做得蠻好的，所以其實只有第一次提交有改到 Haskell code 的改動時會需要去把整包編好，其他時候就直接用快取的執行檔，那這大概一分鐘之內就能做完。</p> |
322 | | -<h3 id="結論">結論</h3> |
323 | | -<p>還是用 Python 做這種事情會比較快：</p> |
324 | | -<ul> |
325 | | -<li>比較多人用：Discogs 有提供 Python SDK，甚至不用自己解析 API response。</li> |
326 | | -<li>Github workflow 設定起來比較不麻煩，而且不會需要花老半天編譯</li> |
327 | | -<li>JSON support</li> |
328 | | -</ul> |
329 | | -<p>不過如果你時間很多的話也是個不錯的體驗啦… 所有的程式碼都在 <a href="https://github.com/usefulalgorithm/usefulalgorithm.github.io/tree/main/scripts/pull_album_info">這裡</a>。</p> |
330 | | - </section> |
331 | | -</article> |
332 | | -]]></summary> |
333 | | -</entry> |
334 | 285 |
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335 | 286 | </feed> |
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