In the
k programming language,
atom is the
monadic case of
@.
@x returns 1 if x is an atom, 0 otherwise; atoms are single characters, integers, floats (floating point numbers), symbols, dictionaries, null, and lambdas.
Non-atoms are vectors, arrays, and lists of all types.
Illustrated at the k command prompt (user input indented 2 spaces, results flush left):
atomlist:(1;-1;0.0;.();_n;;`a;"a")
atomlist
(1;-1;0.0;.();;;`a;"a")
@atomlist
0
@:'atomlist
1 1 1 1 1 1 1 1
@1 2 3
0
@"cat"
0
a:3 2#!3*2
a
(0 1
2 3
4 5)
@a
0
@:'a
0 0 0
@:''a
(1 1
1 1
1 1)