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+*View this file with results and syntax highlighting [here](https://mlochbaum.github.io/BQN/help/prefixes_take.html).*
+
+# Up Arrow (`↑`)
+    
+## `↑ 𝕩`: Prefixes
+    
+Prefixes of array `𝕩` along its first axis.
+    
+           ↑ 1‿2‿3‿4
+
+           a ← 3‿3 ⥊ ↕9
+
+           ↑ a
+
+    
+    
+## `𝕨 ↑ 𝕩`: Take
+    
+For each integer in `𝕨`, take that many elements from each dimension of `𝕩`.
+    
+Negative numbers take from the end.
+    
+If any of the elements in `𝕨` are greater than the length of their respective dimension, the dimension is extended with a fill value.
+    
+          3 ↑ 1‿3‿5‿67
+
+          a ← 4‿4 ⥊ ↕16
+
+          3‿3 ↑ a
+
+          5‿5 ↑ a
+
+          3‿¯3 ↑ a
+
+