$ -pretty -base
the deep analogue of $!. In the expression f $!! x, x is fully evaluated before the function f is applied to it.
Above; if there is no overlap it "dovetails" the two
Above, without dovetailing.
Sequential function application. The argument is evaluated using the given strategy before it is given to the function.
Parallel function application. The argument is evaluated using the given strategy, in parallel with the function application.
The expression f <$$> p creates a fresh permutation parser consisting of parser p. The the final result of the permutation parser is the function f applied to the return value of p. The parser p is not allowed to accept empty input - use the optional combinator (<$?>) instead.
If the function f takes more than one parameter, the type variable b is instantiated to a functional type which combines nicely with the adds parser p to the (<||>) combinator. This results in stylized code permutation parser starts with a combining function f followed by the parsers. The function f gets its parameters in the order in which the parsers are specified, but actual input can be in any order.
The expression f <$?> (x,p) creates a fresh permutation parser consisting of parser p. The the final result of the permutation parser is the function f applied to the return value of p. The parser p is optional - if it can not be applied, the default value x will be used instead.