Dyadic filter

Returns elements from y for which x expression is true.

Syntax: x filter y; filter[x;y]

o)(0=x mod 2)filter x:1 5 6 8 11 17 20 21
6 8 20
o)filter[0=x mod 2;x:1 5 6 8 11 17 20 21]
6 8 20
o)(x>10)filter x:1 5 6 8 11 17 20 21
11 17 20 21
o)