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    <p>It will help to look at your examples through the lens of <code>macroexpand</code>, an essential tool for debugging macros.</p> <p>Example 1:</p> <pre><code>(defmacro triple-do [form] (list 'do form form form)) user=&gt; (triple-do (println "test")) </code></pre> <p>Remember macros are supposed to return a list that will be executed at runtime. Let's see what this macro returns: </p> <pre><code>(macroexpand '(triple-do (println "test"))) ;; (do (println "test") (println "test") (println "test")) </code></pre> <p>So it doesn't execute the code but rather returns a list that represents the code that will be executed once the macro is expanded. This is similar to trying the following snippet at the REPL:</p> <pre><code>(+ 1 2 3) ;; 6 (list '+ 1 2 3) ;; (+ 1 2 3) </code></pre> <p>With this in mind, let's turn to Example 2:</p> <pre><code>(defmacro triple-do [form] (do form form form)) user=&gt; (triple-do (println "test")) </code></pre> <p>Notice how the macro now doesn't return a list. It simply executes the <code>do</code> form which returns the last statement which is the form passed in. This can be easily seen by expanding the macro:</p> <pre><code>(macroexpand '(triple-do (println "test"))) ;; (println "test") </code></pre> <p>That's why you end up with a single print statement.</p> <p>This should give you a clue about Example 3:</p> <pre><code>(defmacro test-macro [form] (do form (println "hard code test"))) user=&gt; (test-macro (println "hello")) </code></pre> <p>It's a bit trickier but let's expand it nevertheless:</p> <pre><code>(macroexpand '(test-macro (println "hello"))) ;; hard code test &lt;= this gets print before the macro fully expands ;; nil &lt;= the expansion yields nil </code></pre> <p>Again, since you're not returning a list but rather simply executing a <code>do</code> form, it simply runs the <code>println</code> call from within the macro and since <code>println</code> returns nil, that becomes the result of the expansion.</p> <p>To illustrate my point, this is how you'd have to rewrite your macro in order to achieve the desired behaviour:</p> <pre><code>(defmacro test-macro [form] (list 'do form (println "hard code test"))) (test-macro (println "hello")) ;; hard code test ;; hello </code></pre> <p>I hope this clears things for you.</p> <p>Just remember this: <em>macros are supposed to return lists that represent the code you'd like to be executed at runtime</em>.</p>
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    1. COthanks leonardoborges. it is clear for me
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    2. COI'm glad it helped. Please consider accepting this answer if it cleared things up enough for you. Thanks.
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