end
+<a id=dollar></a>
### $ Syntax ###
Haskell has a useful bit of syntax that we will adopt. They use `$` as an infix operator that has the same kind of effect as Russell & Whitehead's period. It is semantically inert, and only affects grouping. It enables you to avoid some parentheses in lots of situations. For example, if you want to check that a sequence `xs` is not empty, you'd express that like this: