Chapter 3 Questions

How do I write multi-line strings?

"like\n\
\this,\n\
\see?"

"Here is a backslant \\ as well as \137, \
\a numeric escape character, and \ˆX, a control character."

What are the quoting rules?

• Haskell has the standard escape sequences \a, \b, \f, \n, \r, \t, \v. Control characters are represented as \^X (for control x). Numeric escape codes for Unicode code points exist in decimal \135, octal \o137, and hex \x37.

How do I write a raw string (a string that doesn’t expand escape sequences, but treats them literally)?

• https://hackage.haskell.org/package/raw-strings-qq

  {-# LANGUAGE QuasiQuotes #-}
  import Text.RawString.QQ
  putStrLn $ "regex is" ++ [r|\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,3}|]
  

Is there anything similar to a triple quoted string, or heredoc, that I can use to quote a block of text and indent it properly without including that extra leading indentation in the string itself?

• Using the Text.Heredoc package, from https://hackage.haskell.org/package/heredoc-0.2.0.0/docs/Text-Heredoc.html, you can instead do:

  {-# LANGUAGE QuasiQuotes #-}
  import Text.Heredoc
  famousQuote =
    [str|Any dictator would admire the
        |uniformity and obedience of the U.S. media.
        |  -- Noam Chomsky
        |]
  

Are unix paths represented as strings? If not, what type do they use and how does that behave?

What string types are available? Which are widely used?

See http://dev.stephendiehl.com/hask/#strings for a starting point.

Why is the performance of String “hilariously terrible”, as Stephen Diehl puts it, in comparison to Text?

Is there a way to use Text instead of String by default?

Is there a way to move string processing to compile time?

Why is OverloadedStrings needed?

What is QuasiQuotes?

What is TemplateHaskell?

Does Haskell have a nice templating engine like Pythons Jinja2?