docs/help/prefixes_take.html


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  <title>BQN: Up Arrow (↑)</title>
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<h1 id="up-arrow-"><a class="header" href="#up-arrow-">Up Arrow (<code><span class='Function'>↑</span></code>)</a></h1>
<h2 id="-𝕩-prefixes"><a class="header" href="#-𝕩-prefixes"><code><span class='Function'>↑</span> <span class='Value'>𝕩</span></code>: Prefixes</a></h2>
<p>Prefixes of array <code><span class='Value'>𝕩</span></code> along its first axis.</p>
<a class="replLink" title="Open in the REPL" target="_blank" href="https://mlochbaum.github.io/BQN/try.html#code=ICAg4oaRIDHigL8y4oC/M+KAvzQKCiAgIGEg4oaQIDPigL8zIOKliiDihpU5CgogICDihpEgYQ==">↗️</a><pre>       <span class='Function'>↑</span> <span class='Number'>1</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>3</span><span class='Ligature'>‿</span><span class='Number'>4</span>
⟨ ⟨⟩ ⟨ 1 ⟩ ⟨ 1 2 ⟩ ⟨ 1 2 3 ⟩ ⟨ 1 2 3 4 ⟩ ⟩

       <span class='Value'>a</span> <span class='Gets'>←</span> <span class='Number'>3</span><span class='Ligature'>‿</span><span class='Number'>3</span> <span class='Function'>⥊</span> <span class='Function'>↕</span><span class='Number'>9</span>

       <span class='Function'>↑</span> <span class='Value'>a</span>
┌─                                    
· ↕0‿3 ┌─        ┌─        ┌─         
       ╵ 0 1 2   ╵ 0 1 2   ╵ 0 1 2    
               ┘   3 4 5     3 4 5    
                         ┘   6 7 8    
                                   ┘  
                                     ┘
</pre>
<h2 id="𝕨--𝕩-take"><a class="header" href="#𝕨--𝕩-take"><code><span class='Value'>𝕨</span> <span class='Function'>↑</span> <span class='Value'>𝕩</span></code>: Take</a></h2>
<p>For each integer in <code><span class='Value'>𝕨</span></code>, take that many elements from each dimension of <code><span class='Value'>𝕩</span></code>.</p>
<p>Negative numbers take from the end.</p>
<p>If any of the elements in <code><span class='Value'>𝕨</span></code> are greater than the length of their respective dimension, the dimension is extended with a fill value.</p>
<a class="replLink" title="Open in the REPL" target="_blank" href="https://mlochbaum.github.io/BQN/try.html#code=ICAzIOKGkSAx4oC/M+KAvzXigL82NwoKICBiIOKGkCA04oC/NCDipYog4oaVMTYKCiAgM+KAvzMg4oaRIGIKCiAgNeKAvzUg4oaRIGIKCiAgM+KAv8KvMyDihpEgYg==">↗️</a><pre>      <span class='Number'>3</span> <span class='Function'>↑</span> <span class='Number'>1</span><span class='Ligature'>‿</span><span class='Number'>3</span><span class='Ligature'>‿</span><span class='Number'>5</span><span class='Ligature'>‿</span><span class='Number'>67</span>
⟨ 1 3 5 ⟩

      <span class='Value'>b</span> <span class='Gets'>←</span> <span class='Number'>4</span><span class='Ligature'>‿</span><span class='Number'>4</span> <span class='Function'>⥊</span> <span class='Function'>↕</span><span class='Number'>16</span>

      <span class='Number'>3</span><span class='Ligature'>‿</span><span class='Number'>3</span> <span class='Function'>↑</span> <span class='Value'>b</span>
┌─        
╵ 0 1  2  
  4 5  6  
  8 9 10  
         ┘

      <span class='Number'>5</span><span class='Ligature'>‿</span><span class='Number'>5</span> <span class='Function'>↑</span> <span class='Value'>b</span>
┌─               
╵  0  1  2  3 0  
   4  5  6  7 0  
   8  9 10 11 0  
  12 13 14 15 0  
   0  0  0  0 0  
                ┘

      <span class='Number'>3</span><span class='Ligature'>‿</span><span class='Number'>¯3</span> <span class='Function'>↑</span> <span class='Value'>b</span>
┌─         
╵ 1  2  3  
  5  6  7  
  9 10 11  
          ┘
</pre>