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_ Cut, cut

_ (cut operator)

Cut a list or table into sub-arrays

x _ y     _[x;y]

Where

  • x is a non-decreasing list of integers in the domain til count y
  • y is a list or table

returns y cut at the indexes given in x. The result is a list with the same count as x.

Examples using cut on lists: 

q)2 4 9 _ til 10           /first result item starts at index 2
2 3
4 5 6 7 8
,9
q)
q)2 4 4 9 _ til 10         /cuts are empty for duplicate indexes
2 3
`long$()
4 5 6 7 8
,9
q)2 5 7 _ til 12
2 3 4
5 6
7 8 9 10 11
Example using cut on table sp created using sp.q 
q)\l sp.q
q)count sp
12
q){}show each 2 5 7_sp / `show` returns the generic null ::
s  p  qty
---------
s1 p3 400
s1 p4 200
s4 p5 100
s  p  qty
---------
s1 p6 100
s2 p1 300
s  p  qty
---------
s2 p2 400
s3 p2 200
s4 p2 200
s4 p4 300
s1 p5 400

_(cut) is a multithreaded primitive.

Avoid confusion with underscores in names: separate the Cut operator with spaces.

cut (keyword)

Cut a list or table into a matrix of x columns

x cut y     cut[x;y]

Where

  • x is an integer atom
  • y is a list

returns y splits into a list of lists, all (except perhaps the last) of count x.

q)4 cut til 10
0 1 2 3
4 5 6 7
8 9

Otherwise cut behaves as _ Cut.

Drop