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261 lines
10 KiB
261 lines
10 KiB
11 months ago
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<title>Julio Biason .Me 4.3</title>
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<div class="container sidebar-sticky">
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<div class="sidebar-about">
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<a href="https://blog.juliobiason.me"><h1>Julio Biason .Me 4.3</h1></a>
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<p class="lead">Old school dev living in a 2.0 dev world</p>
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<li class="sidebar-nav-item"><a href="/">English</a></li>
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<li class="sidebar-nav-item"><a href="/pt">Português</a></li>
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<li class="sidebar-nav-item"><a href="/tags">Tags (EN)</a></li>
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<li class="sidebar-nav-item"><a href="/pt/tags">Tags (PT)</a></li>
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<div class="content container">
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<div class="post">
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<h1 class="post-title">Realm of Racket: Lean to Program, One Game at a Time!</h1>
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<span class="post-date">
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2020-12-18
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<a href="https://blog.juliobiason.me/tags/books/">#books</a>
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<a href="https://blog.juliobiason.me/tags/reviews/">#reviews</a>
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<a href="https://blog.juliobiason.me/tags/it/">#it</a>
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<a href="https://blog.juliobiason.me/tags/racket/">#racket</a>
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<a href="https://blog.juliobiason.me/tags/books-2020/">#books:2020</a>
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<a href="https://blog.juliobiason.me/tags/stars-2/">#stars:2</a>
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<a href="https://blog.juliobiason.me/tags/published-2013/">#published:2013</a>
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</span>
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<p><a href="https://www.goodreads.com/book/show/17153511-realm-of-racket">GoodReads Summary</a>:
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Racket is a descendant of Lisp, a programming
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language renowned for its elegance, power, and challenging learning
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curve. But while Racket retains the functional goodness of Lisp, it
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was designed with beginning programmers in mind. Realm of Racket is
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your introduction to the Racket language.</p>
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<span id="continue-reading"></span><div>
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★★☆☆☆
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</div>
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<p>This is a weird book. Not because its content, or the topic at hand,
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but the path chosen to explain things. For example, even after reading
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the whole book, I don't have any idea why I should pick Racket over
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any other Lisp variant.</p>
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<p>So, laundry list of things that put me off:</p>
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<ul>
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<li>
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<p>No real explanation on why I should pick Racket over any other Lisp
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(or any other language, for that matter); they don't say it's faster,
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or more accurate, or it's syntax makes you write less bugs or the
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compiler will prevent you from doing it so.</p>
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</li>
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<li>
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<p>There is a strong favouritism for Racket. It isn't that unexpected,
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but they authors start by bashing other languages, which gives a
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feeling that they just want to make their favourite language look
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better (this goes away only in the last chapter, when comparing Racket
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to Java).</p>
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</li>
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<li>
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<p>They use different words for common things. There isn't and IDE, it
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is a PDE, "program development environment"; the integrated
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development environment becomes "interactive development
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environment"; functions don't "receive" parameters, they "consume"
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the values, which make it sound more like a Rust thing, in which the
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function gets the ownership of the value and, on its end, the memory
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is freed, which doesn't happen in Racket.</p>
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</li>
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<li>
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<p>There is a bunch of "trivial", "simple", and such. This is bad,
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specially if you want newbies to read the book; if they don't grasp
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the concept, saying it is "trivial" will make them feel bad about
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themselves.</p>
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</li>
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<li>
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<p>A lot of explanations are basically "(+ a 1)" -> "adds 1 to
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a". Sure, one may not understand all the facets of the code, but
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when you explain "why" you wrote code that way instead of "what" the
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code is, it is a lot easier to understand.</p>
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</li>
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<li>
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<p>Because the book is too focused on explaining one single library,
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some things feel like "if everything you have is a hammer". For
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example, there is one game of attacking monsters and which the
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authors put the target in the state, and it doesn't feel like this
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should be part of the state of the game. Sure, the selected target
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affects the state, but it is not part of the state, at least for me,
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and there isn't any good explanation on why it should be part of it.</p>
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</li>
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<li>
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<p>Another example uses a complex number to represent points in a 2D
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plane. Sure, 2D points and complex numbers are composed by two
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elements, but that doesn't mean that 2D points <strong>are</strong> complex
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numbers. Types matter, even in dynamic languages.</p>
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</li>
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</ul>
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<p>So... yeah, I think I learn a bit of Racket, but I still don't know
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why I should pick it over anything else. Is it just the game building
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library? Should one pick a language exclusively because of some built
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in library? Doesn't anything else affects this decision? (All
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questions are rhetorical, it is obvious that you shouldn't pick a
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language just because one library).</p>
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<hr />
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<p>Highlights:</p>
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<blockquote>
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<p><code>(foo)*g++.baz(!&qux::zip->ding());</code></p>
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</blockquote>
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<p>"Let me write a very contrived example, just to make my favourite
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language look better compared to this one."</p>
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<blockquote>
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<p><code>(sqrt (+ (sqr 3) (sqr 4)))</code></p>
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</blockquote>
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<p>This is nowhere <em>near</em> the example in C++. If you want to compare
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languages, at least write the same thing.</p>
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<blockquote>
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<p>If you’re on a *nix box, you are already a hero and don’t need instructions.</p>
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</blockquote>
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<p>What a load of bull. It sounds more like you don't have an idea on how
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to do it in Linux.</p>
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<blockquote>
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<p>(the compiler) DrRacket reads this expression, evaluates it,
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prints the result, and then displays its prompt again.</p>
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</blockquote>
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<p>You just described an interpreter, not a compiler. For all purposes
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and intents, sure, it compiles the code to make sure it is not
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invalid, but the concept of "compiler" is used mostly for things that
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take a source and produce a stand-alone executable. Otherwise, even
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Python have a compiler.</p>
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<blockquote>
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<p>the function uses a set! expression to change the value of a
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variable.</p>
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</blockquote>
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<p>Why <code>set!</code>? Why not just <code>set</code>? What the <code>!</code> means? Nothing? Is it
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just a convention?</p>
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<blockquote>
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<p>Racket has three kinds of comments </p>
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</blockquote>
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<p>And absolutely no example of those kinds.</p>
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<blockquote>
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<pre style="background-color:#2b303b;color:#c0c5ce;"><code><span>(/ 4 6)
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</span><span>2/3```
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</span></code></pre>
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</blockquote>
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<p>This is one cool thing: Racket keeps the values in their fractional
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format.</p>
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<blockquote>
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<pre style="background-color:#2b303b;color:#c0c5ce;"><code><span>(struct student (name id# dorm))
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</span><span>(student-name freshman1)
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</span><span>'Joe
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</span><span>(student-id# freshman1)
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</span><span>1234
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</span></code></pre>
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</blockquote>
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<p>Creating structs and extracting values from them.</p>
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<blockquote>
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<pre style="background-color:#2b303b;color:#c0c5ce;"><code><span>(define x 7)
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</span><span> (cond [(= x 7) 5]
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</span><span> [(odd? x) 'odd-number]
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</span><span> [else 'even-number])
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</span></code></pre>
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</blockquote>
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<p>Multiple tests. Also, there is this use of brackets ("[") and
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parenthesis ("(") which is never properly explained, though.</p>
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<blockquote>
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<pre style="background-color:#2b303b;color:#c0c5ce;"><code><span>(when (and file-modified (ask-user-about-saving)) (save-file))
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</span></code></pre>
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</blockquote>
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<p>Because <code>and</code> and <code>or</code> return the value if it's not the boolean false
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(<code>#f</code>), you can use tests to simplify the code.</p>
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<blockquote>
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<pre style="background-color:#2b303b;color:#c0c5ce;"><code><span>(define filename "my-first-program.rkt")
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</span><span>(unless (ask-user-whether-to-keep-file filename) (delete-file filename))
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</span></code></pre>
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</blockquote>
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<p><code>unless</code> is a form of <code>if</code> that performs an action only if the value
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is <code>#f</code> (false).</p>
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<blockquote>
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<pre style="background-color:#2b303b;color:#c0c5ce;"><code><span>(struct orc monster (club))
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</span><span>(struct hydra monster ())
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</span><span>(struct slime monster (sliminess))
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</span><span>(struct brigand monster ())
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</span></code></pre>
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</blockquote>
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<p>Examples of deriving structs from other structs.</p>
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<blockquote>
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<p>In summary, mutators make programming complex </p>
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</blockquote>
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<p>Just a few paragraphs better, you used a mutator saying that this
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would make the code better.</p>
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<blockquote>
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<p><code>raco exe -l hello-world.rkt</code></p>
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</blockquote>
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<p>Generating a standalone executable from Racket source code.</p>
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<blockquote>
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<pre style="background-color:#2b303b;color:#c0c5ce;"><code><span>(define snake%
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</span><span> (class object%
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</span><span> (super-new)
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</span><span> (init-field dir head tail)
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</span><span> (define/public (slither)
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</span><span> (set! tail (cons head (all-but-last tail)))
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</span><span> (set! head (next-head)))
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</span></code></pre>
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</blockquote>
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<p>Classes in Racket.</p>
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