Display a value in a human-readable format. This is the opposite of the Show class which is intended for programmers to read. See Display for how to use this for your own types.

• Writing to file or output: The Builder can be written directly to a handle with hPutBuilder very efficiently as UTF-8. This is the preferred method when writing to stdout or a file.
• Writing to a string: Use one of the functions in Conversions like displayByteString or displayString (when needed).

Use the functions in Data.ByteString.Builder for hex encodings of numbers and strings.

To append Builder you can use the Monoid instance, for example to print things comma-separated, you can use intersperse and mconcat:

mconcat (intersperse ", " (map display [1, 4, 5]))

This example requires the OverloadedStrings language extension.

Display to a ByteString value.

Display to a ByteString value.

Display to a String value. Very inefficient. Only use when you are forced to by another API.

Display to a Text value. Inefficient. Only use when you have to.

Display to a Text value. Inefficient. Only use when you have to.

Display a value in a human-readable format. This is the opposite of the Show class which is intended for programmers to read, and can be used alongside Show.

For example, consider: Maybe String

>>> show (Just "abc")
Just "abc"
>>> show Nothing
Nothing

whereas display is meant for printing to users, so you might write this:

>>> display (Just "abc")
abc
>>> display Nothing
""

You can safely use newtype deriving with this type, e.g.

newtype Name = Name Text deriving (Show, Display)

Instances for exceptions can be written like this:

data MyException = SomeProblem deriving (Show, Typeable)
instance Exception MyException where displayException = displayString