Data.Convertible.Utils

Documentation

boundedConversion

Arguments

:: (Bounded b, Show a, Show b, Convertible a Integer, Convertible b Integer, Typeable a, Typeable b)

=> (a -> ConvertResult b)

Function to do the conversion

-> a

Input data

-> ConvertResult b

Result

Utility function to perform bounds checking as part of a conversion.

Does this be examining the bounds of the destination type, converting to the type of the source via safeConvert, comparing to the source value. Results in an error if the conversion is out of bounds.

convertVia

Arguments

:: (Convertible a b, Convertible b c)

=> b

Dummy data to establish intermediate type - can be undefined

-> a

Input value

-> ConvertResult c

Result

Useful for defining conversions that are implemented in terms of other conversions via an intermediary type. Instead of:

instance Convertible CalendarTime POSIXTime where
    safeConvert a = do r <- safeConvert a
                       safeConvert (r :: ClockTime)

we can now write:

instance Convertible CalendarTime POSIXTime where
    safeConvert = convertVia (undefined::ClockTime)

which does the same thing -- converts a CalendarTime to a ClockTime, then a ClockTime to a POSIXTime, both using existing Convertible instances.