foundation-0.0.25: Alternative prelude with batteries and no dependencies

Safe Haskell | None
Language | Haskell2010

Foundation.String.Read

Synopsis

- readInteger :: String -> Maybe Integer
- readIntegral :: (HasNegation i, IntegralUpsize Word8 i, Additive i, Multiplicative i, IsIntegral i) => String -> Maybe i
- readNatural :: String -> Maybe Natural
- readDouble :: String -> Maybe Double
- readRational :: String -> Maybe Rational
- readFloatingExact :: String -> ReadFloatingCallback a -> Maybe a

# Documentation

readInteger :: String -> Maybe Integer Source #

readIntegral :: (HasNegation i, IntegralUpsize Word8 i, Additive i, Multiplicative i, IsIntegral i) => String -> Maybe i Source #

Read an Integer from a String

Consume an optional minus sign and many digits until end of string.

readNatural :: String -> Maybe Natural Source #

Read a Natural from a String

Consume many digits until end of string.

readDouble :: String -> Maybe Double Source #

Try to read a Double

readRational :: String -> Maybe Rational Source #

Try to read a floating number as a Rational

Note that for safety reason, only exponent between -10000 and 10000 is allowed as otherwise DoS/OOM is very likely. if you don't want this behavior, switching to a scientific type (not provided yet) that represent the exponent separately is the advised solution.

readFloatingExact :: String -> ReadFloatingCallback a -> Maybe a Source #

Read an Floating like number of the form:

`-`
  numbers [ `.` numbers ] [ ( `e` | `E` ) [ `-` ] number ]

Call a function with:

- A boolean representing if the number is negative
- The digits part represented as a single natural number (123.456 is represented as 123456)
- The number of digits in the fractional part (e.g. 123.456 => 3)
- The exponent if any

The code is structured as a simple state machine that:

- Optionally Consume a `-` sign
- Consume number for the integral part
- Optionally
- Consume `.`
- Consume remaining digits if not already end of string
- Optionally Consume a `e` or `E` follow by an optional `-` and a number