The example code shows how the transformer version of the Continuation monad can be used to create a combined monad for using continuations and doing I/O. The example builds on examples 18, 19 and 20.

Example 22

This example is discussed in the section: Standard monad transformers.

The example code shows how the transformer version of the Writer monad can be used to create a combined monad for logging and doing I/O. The example adds timestamps to the log entries of the firewall simulator from example 17.

Example 23

This example is discussed in the section: Standard monad transformers.

The example code shows how the transformer version of the Reader monad can be used to create a monad that combines a shared environment with I/O. The example converts the template system of example 16 to use files as templates.

Example 24

This example is discussed in the section: Standard monad transformers.

The example code uses the StateT transformer on the List monad to create a combined monad for doing non-deterministic stateful computations. The example uses the combined monad to solve a logic problem.

Example 25

This example is discussed in the section: An example with multiple monad transformers.

The example code uses the StateT and WriterT transformers on the List monad to create a combined monad for doing non-deterministic stateful computations with logging. The example uses the combined monad to solve the N-queens problem.

Example 26

This example is discussed in the section: Heavy lifting.

The example code demonstrates the use of the lift function and the necessity of managing its use in complex transformer stacks.