toupper is:exact

toUpper :: Char -> Char
base Data.Char GHC.Unicode, protolude Protolude, rio RIO.Char, base-prelude BasePrelude, Cabal-syntax Distribution.Compat.Prelude, ghc-internal GHC.Internal.Unicode, rebase Rebase.Prelude, cabal-install-solver Distribution.Solver.Compat.Prelude
Convert a letter to the corresponding upper-case letter, if any. Any other character is returned unchanged.
toUpper :: Text -> Text
text Data.Text
O(n) Convert a string to upper case, using simple case conversion. The result string may be longer than the input string. For instance, the German "ß" (eszett, U+00DF) maps to the two-letter sequence "SS".
toUpper :: Stream Char -> Stream Char
text Data.Text.Internal.Fusion.Common, jsaddle Data.JSString.Internal.Fusion.Common
O(n) Convert a string to upper case, using simple case conversion. The result string may be longer than the input string. For instance, the German eszett (U+00DF) maps to the two-letter sequence SS. Properties 
unstream . toUpper . stream = toUpper
toUpper :: Text -> Text
text Data.Text.Lazy
O(n) Convert a string to upper case, using simple case conversion. The result string may be longer than the input string. For instance, the German eszett (U+00DF) maps to the two-letter sequence SS.
toUpper :: Text -> Text
rio RIO.Text
O(n) Convert a string to upper case, using simple case conversion. Subject to fusion. The result string may be longer than the input string. For instance, the German "ß" (eszett, U+00DF) maps to the two-letter sequence "SS".
toUpper :: Text -> Text
rio RIO.Text.Lazy
O(n) Convert a string to upper case, using simple case conversion. Subject to fusion. The result string may be longer than the input string. For instance, the German eszett (U+00DF) maps to the two-letter sequence SS.
toUpper :: Textual t => t -> t
mono-traversable Data.Sequences
Convert a textual sequence to upper-case. 
> toUpper "hello world"
"HELLO WORLD"
toUpper :: Char -> Char
word8 Data.Char8
Micro sign/mu (0xb5) and small letter Y with diaeresis (0xff) remain the same.
toUpper :: Word8 -> Word8
word8 Data.Word8
Micro sign/mu (0xb5) and small letter Y with diaeresis (0xff) remain the same.
toUpper :: JSString -> JSString
jsaddle Data.JSString
O(n) Convert a string to upper case, using simple case conversion. Subject to fusion. The result string may be longer than the input string. For instance, the German "ß" (eszett, U+00DF) maps to the two-letter sequence "SS".
toUpper :: LocaleName -> Text -> Text
text-icu Data.Text.ICU
Uppercase the characters in a string. Casing is locale dependent and context sensitive. The result may be longer or shorter than the original.
toUpper :: T -> T
xml-basic Text.HTML.Basic.Character, wraxml Text.HTML.WraXML.String
toUpper :: Char -> Char
unicode-data Unicode.Char.Case.Compat
Convert a letter to the corresponding upper-case letter, if any. Any other character is returned unchanged. It uses the character property Simple_Uppercase_Mapping. See: upperCaseMapping and toUpperString for full upper case conversion. 
toUpper c == Data.Char.toUpper c
toUpper :: Char -> Char
text-latin1 Text.Ascii
Map upper-case ASCII letters to the corresponding lower-case letters, leaving other characters as is.
toUpper :: Char -> Char
text-latin1 Text.Latin1
Map upper-case Latin-1 letters to the corresponding lower-case letters, leaving other characters as is.
toUpper :: Casing a => a -> a
cased Data.Cased