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! Dict

Make a dictionary or keyed table; remove a key from a table

Syntax: x!y, ![x;y]

Where

  • x and y are same-length lists, returns a dictionary in which x is the key and y is the value
  • y is a simple table and x is a member of 1_til count y, returns a keyed table with the first x columns as its key
  • y is a table and x is 0, returns a simple table; i.e. removes the key

Dictionary keys should be distinct (i.e. {x~distinct x}key dict) but no error is signalled if that is not so.

Items of x and y can be of any datatype, including dictionaries and tables.

q)`a`b`c!1 2 3
a| 1
b| 2
c| 3

q)show kt:2!([]name:`Tom`Jo`Tom; city:`NYC`LA`Lagos; eye:`green`blue`brown; sex:`m`f`m)
name city | eye   sex
----------| ---------
Tom  NYC  | green m
Jo   LA   | blue  f
Tom  Lagos| brown m

q)show ku:([]name:`Tom`Jo`Tom; city:`NYC`LA`Lagos)!([]eye:`green`blue`brown; sex:`m`f`m)
name city | eye   sex
----------| ---------
Tom  NYC  | green m
Jo   LA   | blue  f
Tom  Lagos| brown m
q)kt~ku
1b

q)0!kt
name city  eye   sex
--------------------
Tom  NYC   green m
Jo   LA    blue  f
Tom  Lagos brown m

Dict is a uniform function on its right domain.

Errors

error cause
length x and y are not same-length lists
length x is not in 1_ til count y
type y is not a simple table

key, value
Dictionaries & tables
Q for Mortals §5 Dictionaries