Working with strategies

In this recipe, we will use the parallel library. This library provides a set of strategies to allow us to program concurrent tasks easily.

How to do it...

1. Create a new project called working-with-eval with the simple stack template:

        stack new working-with-eval simple

2. Add a dependency on the parallel library in the build-depends sub-section of the executable section. Also add -threaded and -fprof-auto -rtsopts -eventlog to enable multithreading and profiling:

        executable working-with-eval
          hs-source-dirs:      src
          main-is:             Main.hs
          ghc-options:         -threaded -fprof-auto -rtsopts -eventlog
          default-language: Haskell2010
          build-depends:       base >= 4.7 && < 5
                             , parallel

3. Open src/Main.hs. We will be adding our source here. Add the Main module and import the relevant modules:

        moduleMainwhere        import Control.Parallel.Strategies

4. Create a data type...