Kdb Notes¶
Operator (|)¶
The (|) operator can be used to reverse the ordering of the list. In such a case, a single argument is provided:
q) (|) 0 1 2 3 4 5 6 7 8 9
9 8 7 6 5 4 3 2 1 0
The operator works on any type; in particular, it can be used to reverse the letters in a word:
q) (|) "hello"
"olleh"
where¶
More generally, where applied to a vector of integers (or a dictionary with integer values) can be defined as a function returning the number of occurrences of those integers according to the integer values:
q) where `a`b`c`d!til 4
`b`c`c`d`d`d