Documentation

The constructors used to apply attributes to values for terminal output

Implement ToEscapable by composing constructors of the type Escapable. This can be done for any data type with the exception of the following, which already come with an implementation which renders directly to String:

• Char
• ByteString
• ByteString (Lazy)
• Text
• Text (Lazy)
• Double
• Float
• Int
• Integer
• String
• Word
• Word8
• Word16
• Word32
• Word64

{-# LANGUAGE FlexibleInstances #-}

import Data.Monoid ((<>))
import Text.EscapeArtist

type FileName = String
type LineNumber = Integer
type ColumnNumber = Integer

data ErrorType = SyntaxError FileName LineNumber ColumnNumber deriving (Show)

instance ToEscapable ErrorType where
    toEscapable (SyntaxError fn ln cn) = Default "Syntax error in file "
                                       <> FgYellow ^$ Underline fn
                                       <> Default " at "
                                       <> FgRed (show ln ++ ":" ++ show cn)

instance ToEscapable (Either ErrorType String) where
    toEscapable (Left e) = toEscapable e
    toEscapable (Right m) = FgGreen m

mkSyntaxError :: FileName -> LineNumber -> ColumnNumber -> Either ErrorType String
mkSyntaxError fn ln cn = Left $ SyntaxError fn ln cn

mkStatusOK :: Either ErrorType String
mkStatusOK = Right "Status OK"

putEscLn $ mkSyntaxError "some/File.hs" 1 23
putEscLn mkStatusOK

Note: For GHC < 7.10 you will also need to explicitly derive Typeable for custom data types implementing ToEscapable. See the section Explicitly Derived Typeable in the documentation.

Convert any instance of ToEscapable to a String and output it to the terminal followed by a newline

Convert any instance of ToEscapable to a String and output it to the terminal

Convert any instance of ToEscapable to a String

The same as $, but with higher precedence. One level of precedence higher than <>. This allows avoiding parentheses when using $ and <> in the same expression. For example:

Underline $ (Bright $ FgGreen "GREEN") <> Default " " <> FgYellow "YELLOW"

can be written as:

Underline $ Bright ^$ FgGreen "GREEN" <> Default " " <> FgYellow "YELLOW"

In this example, Bright is applied only to the String "GREEN", that is concatenated with a space and the yellow text "YELLOW", then Underline is applied to the entire expression.