Up Arrow (↑)

↑ 𝕩: Prefixes

Prefixes of array 𝕩 along its first axis.

       ↑ 1‿2‿3‿4
⟨ ⟨⟩ ⟨ 1 ⟩ ⟨ 1 2 ⟩ ⟨ 1 2 3 ⟩ ⟨ 1 2 3 4 ⟩ ⟩

       a ← 3‿3 ⥊ ↕9

       ↑ a
┌─                                    
· ↕0‿3 ┌─        ┌─        ┌─         
       ╵ 0 1 2   ╵ 0 1 2   ╵ 0 1 2    
               ┘   3 4 5     3 4 5    
                         ┘   6 7 8    
                                   ┘  
                                     ┘

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
⟨ 1 3 5 ⟩

      a ← 4‿4 ⥊ ↕16
Error: Redefinition

      3‿3 ↑ a
┌─       
╵ 0 1 2  
  3 4 5  
  6 7 8  
        ┘

      5‿5 ↑ a
┌─           
╵ 0 1 2 0 0  
  3 4 5 0 0  
  6 7 8 0 0  
  0 0 0 0 0  
  0 0 0 0 0  
            ┘

      3‿¯3 ↑ a
┌─       
╵ 0 1 2  
  3 4 5  
  6 7 8  
        ┘