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1. data Format1

   vformat	Text.Format

   A variant of Format, it transforms all argument's key to Nest (Index 0) key

2. class FormatArg a

   vformat	Text.Format

   Typeclass of formatable values. The formatArg method takes a value, a key and a field format descriptor and either fails due to a ArgError or produce a string as the result. There is a default formatArg for Generic instances, which applies defaultOptions to genericFormatArg. There are two reasons may cause formatting fail

   1. Can not find argument for the given key.
   2. The field format descriptor does not match the argument.

   Extending to new types

   Those format functions can be extended to format types other than those provided by default. This is done by instantiating FormatArg. Examples

   {-# LANGUAGE DeriveGeneric     #-}
   {-# LANGUAGE OverloadedStrings #-}
   
   import           Control.Exception
   import           GHC.Generics
   import           Text.Format
   
   -- Manually extend to ()
   instance FormatArg () where
   formatArg x k fmt@(ArgFmt{fmtSpecs="U"}) =
   let fmt' = fmt{fmtSpecs = ""}
   in  formatArg (show x) k fmt'
   formatArg _ _ _ = Left $ toException ArgFmtError
   
   -- Use default generic implementation for type with nullary data constructors.
   data Color = Red | Yellow | Blue deriving Generic
   
   instance FormatArg Color
   
   -- Use default generic implementation for type with non-nullary data constructor.
   data Triple = Triple String Int Double deriving Generic
   
   instance FormatArg Triple
   
   -- Use default generic implementation for type using record syntax.
   data Student = Student { no   :: Int
   , name :: String
   , age  :: Int
   } deriving Generic
   
   instance FormatArg Student
   
   -- Customize field names
   data Book = Book { bookName   :: String
   , bookAuthor :: String
   , bookPrice  :: Double
   }
   
   instance FormatArg Book where
   formatArg x k fmt
   | k == mempty = return $ format1 "{name} {author} {price:.2f}" x
   | k == Name "name" = formatArg (bookName x) mempty fmt
   | k == Name "author" = formatArg (bookAuthor x) mempty fmt
   | k == Name "price" = formatArg (bookPrice x) mempty fmt
   | otherwise = Left $ toException $ ArgKeyError
   
   -- A better way to customize field names
   -- instance FormatArg Book where
   --   formatArg = genericFormatArg $
   --     defaultOptions { fieldLabelModifier = drop 4 }
   
   main :: IO ()
   main = do
   putStrLn $ format "A unit {:U}" ()
   putStrLn $ format "I like {}." Blue
   putStrLn $ format "Triple {0!0} {0!1} {0!2}" $ Triple "Hello" 123 pi
   putStrLn $ format1 "Student: {no} {name} {age}" $ Student 1 "neo" 30
   putStrLn $ format "A book: {}" $ Book "Math" "nobody" 99.99
   putStrLn $ format1 "Book: {name}, Author: {author}, Price: {price:.2f}" $
   Book "Math" "nobody" 99.99
   

   Note: Since v0.12.0, FormatTime instance has been remove, use vformat-time instead.

3. class FormatType t

   vformat	Text.Format

   A typeclass provides the variable arguments magic for format

4. type Formatter = ArgKey -> ArgFmt -> Either SomeException String

   vformat	Text.Format

   No documentation available.

5. Forall :: forall t (tp1 :: BaseType) (e :: BaseType -> Type) . !ExprBoundVar t tp1 -> !e BaseBoolType -> NonceApp t e 'BaseBoolType

   what4	What4.Expr

   No documentation available.

6. Forall :: forall t (tp1 :: BaseType) (e :: BaseType -> Type) . !ExprBoundVar t tp1 -> !e BaseBoolType -> NonceApp t e 'BaseBoolType

   what4	What4.Expr.App

   No documentation available.

7. Forall :: forall t (tp1 :: BaseType) (e :: BaseType -> Type) . !ExprBoundVar t tp1 -> !e BaseBoolType -> NonceApp t e 'BaseBoolType

   what4	What4.Expr.Builder

   No documentation available.

8. ForallBound :: BoundQuant

   what4	What4.Expr.VarIdentification

   No documentation available.

9. FormattedString :: Text -> String

   yaml-unscrambler	YamlUnscrambler.Expectations

   Must conform to a textually described format.

10. ForeignFileHeaderPragma :: KindOfForeignCode

    Agda	Agda.Compiler.MAlonzo.Pragmas

    A pragma that must appear before the module header.

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