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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
b ← 4‿4 ⥊ ↕16
3‿3 ↑ b
5‿5 ↑ b
3‿¯3 ↑ b
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