Text.Read.Bounded

Documentation

data BoundedRead a

Information about a bounded read.

Constructors

NoRead

The read failed.

ExactRead a

The value was successfully read exactly, and did not have to be clamped to a narrower representation.

ClampedRead a

The value was successfully read, but had to be clamped to a narrower representation because its value was too wide.

Instances

Eq a => Eq (BoundedRead a)

Ord a => Ord (BoundedRead a)

Read a => Read (BoundedRead a)

Show a => Show (BoundedRead a)

class ReadBounded a where

Much like the Read class, but will return (possibly) clamped values.

Typical instances of this class will clamp against minBound and maxBound

This class is designed to avoid inconsistency problems such as the following:

>>> read "999999999999999999999" :: Int
3875820019684212735
>>> read "9999999999999999999999" :: Int
1864712049423024127

Using this class, the results are predictable and precise:

>>> readBounded "999999999999999999999" :: BoundedRead Int
ClampedRead 9223372036854775807
>>> readBounded "9999999999999999999999" :: BoundedRead Int
ClampedRead 9223372036854775807
>>> readBounded "9223372036854775807" :: BoundedRead Int
ExactRead 9223372036854775807
>>> readBounded "1337" :: BoundedRead Int
ExactRead 1337
>>> readBounded "xxx" :: BoundedRead Int
NoRead

Methods

readBounded :: String -> BoundedRead a

Instances

ReadBounded Int

ReadBounded Int8

ReadBounded Int16

ReadBounded Int32

ReadBounded Int64

ReadBounded Integer

ReadBounded Word

ReadBounded Word8

ReadBounded Word16

ReadBounded Word32

ReadBounded Word64

readBoundedInteger :: (Bounded a, Read a, Integral a) => String -> BoundedRead a

Reads a clamped value for any integer type with the given class constraints. Useful for implementing a ReadBounded instance or avoiding one.