Let 
be a function such that
for any 
,
..., 
, there is at least one 
such that 
. Then the 
-operator 
gives the least number 
such that 
. More generally, for a relation 
, the 
-operator gives the least 
, if any, such that 
is true, and this least value of 
is denoted 
(Mendelson 1997, p. 175).
For example, given a criterion crit and a list 
x1, x2, ..., xn
, the 
-operator could be written in the Wolfram
Language as Select[Sort[
x1, x2, ..., xn
], crit, 1].
