Copyright | (c) The University of Glasgow 2002 |
---|---|

License | BSD-style (see the file libraries/base/LICENSE) |

Maintainer | libraries@haskell.org |

Stability | provisional |

Portability | portable |

Safe Haskell | Trustworthy |

Language | Haskell2010 |

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

-like kind of values.

## Synopsis

- showSigned :: Real a => (a -> ShowS) -> Int -> a -> ShowS
- showIntAtBase :: (Integral a, Show a) => a -> (Int -> Char) -> a -> ShowS
- showInt :: Integral a => a -> ShowS
- showHex :: (Integral a, Show a) => a -> ShowS
- showOct :: (Integral a, Show a) => a -> ShowS
- showEFloat :: RealFloat a => Maybe Int -> a -> ShowS
- showFFloat :: RealFloat a => Maybe Int -> a -> ShowS
- showGFloat :: RealFloat a => Maybe Int -> a -> ShowS
- showFFloatAlt :: RealFloat a => Maybe Int -> a -> ShowS
- showGFloatAlt :: RealFloat a => Maybe Int -> a -> ShowS
- showFloat :: RealFloat a => a -> ShowS
- showHFloat :: 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 :: (Eq a, Num a) => ReadS a
- readOct :: (Eq a, Num a) => ReadS a
- readHex :: (Eq a, Num a) => ReadS a
- readFloat :: RealFrac a => ReadS a
- lexDigits :: ReadS String
- fromRat :: RealFloat a => Rational -> a
- class Fractional a => Floating a where

# 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, Show a) => a -> (Int -> Char) -> a -> ShowS Source #

Shows a *non-negative* `Integral`

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

showHex :: (Integral a, Show a) => a -> ShowS Source #

Show *non-negative* `Integral`

numbers in base 16.

showEFloat :: RealFloat a => Maybe Int -> a -> ShowS Source #

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 -> ShowS Source #

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 -> ShowS Source #

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.

showFFloatAlt :: RealFloat a => Maybe Int -> a -> ShowS Source #

Show a signed `RealFloat`

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

, `0.0015`

).

This behaves as `showFFloat`

, except that a decimal point
is always guaranteed, even if not needed.

*Since: 4.7.0.0*

showGFloatAlt :: RealFloat a => Maybe Int -> a -> ShowS Source #

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.

This behaves as `showFFloat`

, except that a decimal point
is always guaranteed, even if not needed.

*Since: 4.7.0.0*

showFloat :: RealFloat a => a -> ShowS Source #

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.

showHFloat :: RealFloat a => a -> ShowS Source #

Show a floating-point value in the hexadecimal format,
similar to the `%a`

specifier in C's printf.

`>>>`

"0x1.a86b851eb851fp7"`showHFloat (212.21 :: Double) ""`

`>>>`

"-0x1.9851ecp3"`showHFloat (-12.76 :: Float) ""`

`>>>`

"-0x0p+0"`showHFloat (-0 :: Double) ""`

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 a Source #

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.

readDec :: (Eq a, Num a) => ReadS a Source #

Read an unsigned number in decimal notation.

`>>>`

[(644,"")]`readDec "0644"`

readOct :: (Eq a, Num a) => ReadS a Source #

Read an unsigned number in octal notation.

`>>>`

[(420,"")]`readOct "0644"`

readHex :: (Eq a, Num a) => ReadS a Source #

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

`>>>`

[(3735928559,"")]`readHex "deadbeef"`

readFloat :: RealFrac a => ReadS a Source #

Reads an *unsigned* `RealFrac`

value,
expressed in decimal scientific notation.

# Miscellaneous

class Fractional a => Floating a where Source #

Trigonometric and hyperbolic functions and related functions.

The Haskell Report defines no laws for `Floating`

. However, `(`

, `+`

)`(`

and `*`

)`exp`

are customarily expected to define an exponential field and have
the following properties:

`exp (a + b)`

=`exp a * exp b`

`exp (fromInteger 0)`

=`fromInteger 1`

(**) :: a -> a -> a infixr 8 Source #

logBase :: a -> a -> a Source #

computes `log1p`

x

, but provides more precise
results for small (absolute) values of `log`

(1 + x)`x`

if possible.

*Since: 4.9.0.0*

computes `expm1`

x

, but provides more precise
results for small (absolute) values of `exp`

x - 1`x`

if possible.

*Since: 4.9.0.0*