base-4.3.1.0: Basic libraries

Portability | portable
Stability | provisional
Maintainer | libraries@haskell.org

Numeric

Contents

- Showing
- Reading
- Miscellaneous

Description

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 => 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

showSigned

Arguments

:: 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 -> ShowS

Shows a non-negative `Integral` number using the base specified by the first argument, and the character representation specified by the second.

showInt :: Integral a => a -> ShowS

Show non-negative `Integral` numbers in base 10.

showHex :: Integral a => a -> ShowS

Show non-negative `Integral` numbers in base 16.

showOct :: Integral a => a -> ShowS

Show non-negative `Integral` numbers in base 8.

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

Show a signed `RealFloat` value using scientific (exponential) notation (e.g. `2.45e2`, `1.5e-3`).

In the call ``showEFloat` digs val`, if `digs` is `Nothing`, the value is shown to full precision; if `digs` is ``Just` d`, then at most `d` digits after the decimal point are shown.

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

Show a signed `RealFloat` value using standard decimal notation (e.g. `245000`, `0.0015`).

In the call ``showFFloat` digs val`, if `digs` is `Nothing`, the value is shown to full precision; if `digs` is ``Just` d`, then at most `d` digits after the decimal point are shown.

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

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 ``showGFloat` digs val`, if `digs` is `Nothing`, the value is shown to full precision; if `digs` is ``Just` d`, then at most `d` digits after the decimal point are shown.

showFloat :: RealFloat a => a -> ShowS

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)

`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

1.     n >= 1

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

3.     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

Reads a signed `Real` value, given a reader for an unsigned value.

readInt

Arguments

:: 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 `Int`
-> ReadS a |

Reads an unsigned `Integral` value in an arbitrary base.

readDec :: Num a => ReadS a

Read an unsigned number in decimal notation.

readOct :: Num a => ReadS a

Read an unsigned number in octal notation.

readHex :: Num a => ReadS a

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

readFloat :: RealFrac a => ReadS a

Reads an unsigned `RealFrac` value, expressed in decimal scientific notation.

lexDigits :: ReadS String

Reads a non-empty string of decimal digits.

# Miscellaneous

fromRat :: RealFloat a => Rational -> a

Converts a `Rational` value into any type in class `RealFloat`.