Turtle.Format

Minimalist implementation of type-safe formatted strings, borrowing heavily from the implementation of the formatting package.

Example use of this module:

>>> :set -XOverloadedStrings
>>> import Turtle.Format
>>> format ("This is a "%s%" string that takes "%d%" arguments") "format" 2
"This is a format string that takes 2 arguments"

A Format string that takes no arguments has this type:

 "I take 0 arguments" :: Format r r

 format "I take 0 arguments" :: Text

>>> format "I take 0 arguments"
"I take 0 arguments"

A Format string that takes one argument has this type:

 "I take "%d%" arguments" :: Format r (Int -> r)

 format ("I take "%d%" argument") :: Int -> Text

>>> format ("I take "%d%" argument") 1
"I take 1 argument"

A Format string that takes two arguments has this type:

 "I "%s%" "%d%" arguments" :: Format r (Text -> Int -> r)

 format ("I "%s%" "%d%" arguments") :: Text -> Int -> Text

>>> format ("I "%s%" "%d%" arguments") "take" 2
"I take 2 arguments"

Format

data Format a b

A Format string

Instances

Category Format

~ * a b => IsString (Format a b)

(%) :: Format b c -> Format a b -> Format a c

Concatenate two Format strings

format :: Format Text r -> r

Convert a Format string to a print function that takes zero or more typed arguments and returns a Text string

makeFormat :: (a -> Text) -> Format r (a -> r)

Create your own format specifier

Parameters

w :: Show a => Format r (a -> r)

Format any Showable value

>>> format w True
"True"

d :: Format r (Int -> r)

Format an Int value as a signed decimal

>>> format d 25
"25"
>>> format d (-25)
"-25"

u :: Format r (Word -> r)

Format a Word value as an unsigned decimal

>>> format u 25
"25"

o :: Format r (Word -> r)

Format a Word value as an unsigned octal number

>>> format o 25
"31"

x :: Format r (Word -> r)

Format a Word value as an unsigned hexadecimal number (without a leading "0x")

>>> format x 25
"19"

f :: Format r (Double -> r)

Format a Double using decimal notation with 6 digits of precision

>>> format f 25.1
"25.100000"

e :: Format r (Double -> r)

Format a Double using scientific notation with 6 digits of precision

>>> format e 25.1
"2.510000e1"

g :: Format r (Double -> r)

Format a Double using decimal notation for small exponents and scientific notation for large exponents

>>> format g 25.1
"25.100000"
>>> format g 123456789
"1.234568e8"
>>> format g 0.00000000001
"1.000000e-11"

s :: Format r (Text -> r)

Format that inserts Text

>>> format s "ABC"
"ABC"

fp :: Format r (FilePath -> r)

Format a FilePath into Text

Utilities

repr :: Show a => a -> Text

Convert a Showable value to Text

Short-hand for (format w)

>>> repr (1,2)
"(1,2)"