Portability | portable |
---|---|

Stability | provisional |

Maintainer | libraries@haskell.org |

Odds and ends, mostly functions for reading and showing
`RealFloat`

-like kind of values.

- showSigned :: Real a => (a -> ShowS) -> Int -> a -> ShowS
- showIntAtBase :: Integral a => a -> (Int -> Char) -> a -> ShowS
- showInt :: Integral a => a -> ShowS
- showHex :: Integral a => a -> ShowS
- showOct :: Integral a => a -> ShowS
- showEFloat :: RealFloat a => Maybe Int -> a -> ShowS
- showFFloat :: RealFloat a => Maybe Int -> a -> ShowS
- showGFloat :: RealFloat a => Maybe Int -> a -> ShowS
- showFloat :: RealFloat a => a -> ShowS
- floatToDigits :: RealFloat a => Integer -> a -> ([Int], Int)
- readSigned :: Real a => ReadS a -> ReadS a
- readInt :: Num a => a -> (Char -> Bool) -> (Char -> Int) -> ReadS a
- readDec :: Num a => ReadS a
- readOct :: Num a => ReadS a
- readHex :: Num a => ReadS a
- readFloat :: RealFrac a => ReadS a
- lexDigits :: ReadS String
- fromRat :: RealFloat a => Rational -> a

# Showing

:: Real a | |

=> (a -> ShowS) | a function that can show unsigned values |

-> Int | the precedence of the enclosing context |

-> a | the value to show |

-> ShowS |

Converts a possibly-negative `Real`

value to a string.

showIntAtBase :: Integral a => a -> (Int -> Char) -> a -> ShowSSource

Shows a *non-negative* `Integral`

number using the base specified by the
first argument, and the character representation specified by the second.

showEFloat :: RealFloat a => Maybe Int -> a -> ShowSSource

Show a signed `RealFloat`

value
using scientific (exponential) notation (e.g. `2.45e2`

, `1.5e-3`

).

In the call

, if `showEFloat`

digs val`digs`

is `Nothing`

,
the value is shown to full precision; if `digs`

is

,
then at most `Just`

d`d`

digits after the decimal point are shown.

showFFloat :: RealFloat a => Maybe Int -> a -> ShowSSource

Show a signed `RealFloat`

value
using standard decimal notation (e.g. `245000`

, `0.0015`

).

In the call

, if `showFFloat`

digs val`digs`

is `Nothing`

,
the value is shown to full precision; if `digs`

is

,
then at most `Just`

d`d`

digits after the decimal point are shown.

showGFloat :: RealFloat a => Maybe Int -> a -> ShowSSource

Show a signed `RealFloat`

value
using standard decimal notation for arguments whose absolute value lies
between `0.1`

and `9,999,999`

, and scientific notation otherwise.

In the call

, if `showGFloat`

digs val`digs`

is `Nothing`

,
the value is shown to full precision; if `digs`

is

,
then at most `Just`

d`d`

digits after the decimal point are shown.

showFloat :: RealFloat a => a -> ShowSSource

Show a signed `RealFloat`

value to full precision
using standard decimal notation for arguments whose absolute value lies
between `0.1`

and `9,999,999`

, and scientific notation otherwise.

floatToDigits :: RealFloat a => Integer -> a -> ([Int], Int)Source

`floatToDigits`

takes a base and a non-negative `RealFloat`

number,
and returns a list of digits and an exponent.
In particular, if `x>=0`

, and

floatToDigits base x = ([d1,d2,...,dn], e)

then

n >= 1

x = 0.d1d2...dn * (base**e)

0 <= di <= base-1

# Reading

*NB:* `readInt`

is the 'dual' of `showIntAtBase`

,
and `readDec`

is the `dual' of `showInt`

.
The inconsistent naming is a historical accident.

readSigned :: Real a => ReadS a -> ReadS aSource

Reads a *signed* `Real`

value, given a reader for an unsigned value.

:: Num a | |

=> a | the base |

-> (Char -> Bool) | a predicate distinguishing valid digits in this base |

-> (Char -> Int) | a function converting a valid digit character to an |

-> ReadS a |

Reads an *unsigned* `Integral`

value in an arbitrary base.

readHex :: Num a => ReadS aSource

Read an unsigned number in hexadecimal notation. Both upper or lower case letters are allowed.

readFloat :: RealFrac a => ReadS aSource

Reads an *unsigned* `RealFrac`

value,
expressed in decimal scientific notation.