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Author: seancorfield

articles/language/functions/index.html

@@ -190,14 +190,26 @@ <h2>Language: Functions</h2>
   [{:keys [currency amount]}]
   currency)
 </code></pre><p>The example above assumes that map keys will be keywords and we are interested in two values: <code>currency</code>
-and <code>amount</code>. The same can be done for strings:</p><pre><code class="clojure">(defn currency-of
+and <code>:amount</code>. The same can be done for strings:</p><pre><code class="clojure">(defn currency-of
   [{:strs [currency amount]}]
   currency)
 </code></pre><p>and symbols:</p><pre><code class="clojure">(defn currency-of
   [{:syms [currency amount]}]
   currency)
 </code></pre><p>In practice, keywords are very commonly used for map keys so destructuring with <code>{:keys [...]}</code> is very common
-as well.</p><p>Map destructuring also lets us specify default values for keys that may be missing:</p><pre><code class="clojure">(defn currency-of
+as well.</p><p>If you want to destructure a map that has namespaced keys, you can either
+specify the prefix on each name in the binding or as a prefix on <code>:keys</code> itself:</p><pre><code class="clojure">;; instead of {:currency "GBP" :amount 95.99} let's assume we have namespaced
+;; keys: {:invoice/currency "GBP" :invoice/amount 95.99}
+(defn currency-of
+  [{:keys [invoice/currency invoice/amount]}] ; prefixed names
+  currency) ; bind to unprefixed symbols
+
+;; or
+
+(defn currency-of
+  [{:invoice/keys [currency amount]}] ; prefixed :keys
+  currency) ; bind to unprefixed symbols
+</code></pre><p>Map destructuring also lets us specify default values for keys that may be missing:</p><pre><code class="clojure">(defn currency-of
   [{:keys [currency amount] :or {currency :gbp}}]
   currency)
 </code></pre><p>This is very commonly used for implementing functions that take "extra options" (faking named arguments support).</p><p>Just like with positional destructuring, map destructuring works exactly the same way for let bindings:</p><pre><code class="klipse-clojure nohighlight">(let [money               {:currency :gbp :amount 10}

articles/tutorials/getting_started/index.html

@@ -98,7 +98,7 @@ <h2>Getting Started</h2>
 repositories) without needing JAR files to be built and deployed.</p><p>Since the release of the official Clojure CLI, usage of Leiningen has dropped
 as the community adopted the new CLI and associated libraries such as
 <code>tools.deps</code> and <code>tools.build</code>.
-<em>[See <a href="https://clojure.org/news/2022/06/02/state-of-clojure-2022">State of Clojure 2022 Survey Results</a>]</em></p><p><strong>Too Much Information! What Should I Use?</strong></p><p>As noted above, if you're following a book or tutorial that uses Leiningen,
+<em>[See <a href="https://clojure.org/news/2022/06/02/state-of-clojure-2022">State of Clojure 2022 Survey Results</a> -- and a year later the CLI usage exceeded 70% while Leiningen had dropped to around 60%]</em></p><p><strong>Too Much Information! What Should I Use?</strong></p><p>As noted above, if you're following a book or tutorial that uses Leiningen,
 or working with a project that uses Leiningen, then keep using Leiningen.</p><p>If you're following a book or tutorial that uses the newer CLI, or working
 with a project that uses it, then keep using the Clojure CLI and associated
 libraries.</p><p>If you're starting from scratch, learning the Clojure CLI is probably a

articles/tutorials/introduction/index.html

@@ -148,11 +148,13 @@ <h2>Introduction to Clojure</h2>
 you want to include a double-quote mark in a string, backslash-escape
 it.</p><pre><code class="clojure">#"^foo\d?$"   ; A regular expression.
 :foo          ; A keyword.
+:foo/bar      ; A namespaced keyword.
 </code></pre><p>We'll have more to say about <a href="#regular-expressions">regular
 expressions</a> later on.</p><p>Keywords are just scalars that evaluate to themselves and are useful
 where in other languages you might use little strings as identifiers
 (for example, as the keys in a hashmap). More about keywords in the
-next section (<a href="#data-structures">Data Structures</a>).</p><pre><code class="clojure">'foo   ; A symbol.
+next section (<a href="#data-structures">Data Structures</a>).</p><pre><code class="clojure">'foo     ; A symbol.
+'foo/bar ; A namespaced symbol.
 </code></pre><p>A <em>symbol</em> is an object that represents the <em>name</em> of something. The
 single quote mark is there to keep Clojure from trying to figure out
 to what the symbol refers (the quote isn't part of the identifier of
@@ -172,8 +174,10 @@ <h2>Introduction to Clojure</h2>
 [1 :two "three"]   ; Put anything into them you like.
 {:a 1 :b 2}        ; A hashmap (or just "map", for short).
 </code></pre><p>A hashmap is your typical hash/dictionary data structure. In the above
-example, the keys are :a and :b, and the values are 1 and 2. One key-value
-pair in a map is called an <em>entry</em>.</p><p>Although it's most common to use keywords (as shown above) for hashmap
+example, the keys are <code>:a</code> and <code>:b</code>, and the values are 1 and 2. One key-value
+pair in a map is called an <em>entry</em>.</p><p>Using namespaced keywords as keys is a common practice in Clojure applications,
+as it provides more context to the key and helps avoid key collisions:</p><pre><code class="clojure">{:customer/id 123 :invoice/id "INV-456" :invoice/total 95.99}
+</code></pre><blockquote><p>Note: if you have a hashmap where all the keys have the same namespace prefix, such as <code>{:invoice/id "INV-456" :invoice/total 95.99}</code>, the REPL will print it using a shorthand syntax, where the prefix is shown in front of the hashmap and the keys are shown without the prefix: <code>#:invoice{:id "INV-456", :total 95.99}</code>. This is just a shorthand syntax for printing the hashmap and doesn't affect how you use the hashmap in your code.</p></blockquote><p>Although it's most common to use keywords (as shown above) for hashmap
 keys, you can use any values you like for the keys as well as the
 values.</p><pre><code class="clojure">#{:a :b :c}        ; A set (unordered, and contains no duplicates).
 '(1 2 3)           ; A list (linked-list)

cryogen.xml

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