Text.Scanf

Dead simple and type-safe scanf/printf.

Main definitions

scanf :: Format t -> String -> Maybe t

Parse a string according to a format string.

scanf [fmt|Hello %s|] "Hello world!" :: Maybe (String :+ ())
  = ("world!" :+ ())

printf :: Format t -> t -> String

Print a string according to a format string.

printf [fmt|Hello %s|] ("everyone!" :+ ())
  = "Hello everyone!" 

data a :+ b infixr 1

A pretty pair type to build lists with values of different types. Remember to close lists with ().

3 :+ "14" :+ () :: Int :+ String :+ ()

Constructors

a :+ b infixr 1

Instances

(Eq b, Eq a) => Eq ((:+) a b)

Methods

(==) :: (a :+ b) -> (a :+ b) -> Bool

(/=) :: (a :+ b) -> (a :+ b) -> Bool

(Ord b, Ord a) => Ord ((:+) a b)

Methods

compare :: (a :+ b) -> (a :+ b) -> Ordering

(<) :: (a :+ b) -> (a :+ b) -> Bool

(<=) :: (a :+ b) -> (a :+ b) -> Bool

(>) :: (a :+ b) -> (a :+ b) -> Bool

(>=) :: (a :+ b) -> (a :+ b) -> Bool

max :: (a :+ b) -> (a :+ b) -> a :+ b

min :: (a :+ b) -> (a :+ b) -> a :+ b

(Show b, Show a) => Show ((:+) a b)

Methods

showsPrec :: Int -> (a :+ b) -> ShowS

show :: (a :+ b) -> String

showList :: [a :+ b] -> ShowS

fmt :: QuasiQuoter

Parse a typed Format string.

The following conversion strings are supported:

• %d: signed integer (Int)
• %l: signed integer (Integer, unbounded)
• %f: floating point (Double)
• %s: string of non-space characters (String)
• %c: single character (Char)
• %%: parse/print a literal percent character

N.B.: in scanf, spaces in the format string match any number of whitespace character until the next nonspace character.

[fmt|%d lazy %s and %d strict %s|]
  :: Format (Int :+ String :+ Int :+ String :+ ())

fmt_ :: (Format () -> Format t) -> Format t

Construct a format string. This is an alternative to fmt that doesn't rely on Template Haskell.

The components of a format string are composed using (.) (function composition) and (%) (wrapper for constant strings).

fmt_ (int . " lazy " % string . " and " % int . " strict " % string)
  :: Format (Int :+ String :+ Int :+ String :+ ())

data Format t

Typed scanf/printf format strings. They can be built using the fmt quasiquote or with the fmt_ function and format combinators.

Instances

Show (Format t)

Methods

showsPrec :: Int -> Format t -> ShowS

show :: Format t -> String

showList :: [Format t] -> ShowS

Format constructors

(%) :: String -> (Format t -> Format q) -> Format t -> Format q infixr 9

Append a constant string to a format string component.

N.B.: in scanf, spaces in the format string match any number of whitespace character until the next nonspace character.

integer :: Format t -> Format (Integer :+ t)

Format an Integer.

int :: Format t -> Format (Int :+ t)

Format an Int.

double :: Format t -> Format (Double :+ t)

Format a Double.

string :: Format t -> Format (String :+ t)

Format a String.

char :: Format t -> Format (Char :+ t)

Format a Char.