The C#/LINQ syntax for this is nice for this reason. It's S.Where(P), which makes it clear that the thing on the left is the thing being filtered, and that it's

The C#/LINQ syntax for this is nice for this reason. It's S.Where(P), which makes it clear that the thing on the left is the thing being filtered, and that it's taking values x where P(x) is true. One could also make the argument that it also suggests that it's a non-destructive operation, but that might just be years of familiarity with SQL semantics talking.