Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "Conditionally import Prelude, hiding the reverse function."

A block of code is set as follows:

    reverse :: [a] -> [a]
    reverse xs = reverse' xs []
    where
      reverse' :: [a] -> [a] -> [a]
      reverse' [] rs = rs
      reverse' (x:xs) rs = reverse' xs (x:rs)

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

    main-is: Main.hs
    default-language: Haskell2010
    build-depends: base >= 4.7 && < 5
      , mtl
      , containers

Any command-line input or output is written as follows:

stack build
stack exec -- state-monad

New terms and important words are shown in bold.