hasElem xs x = elem x xs except that
xs is turned
into a
Set first. Use underapplied to speed up subsequent
lookups, e.g.
filter (hasElem xs) ys. Only amortized when
used several times!
Time complexity <math> for <math> lookups in a list of
length <math>. (Compare this to
elem's <math>.)
This is
Agda.Utils.List.hasElem.