Portability | portable |
---|---|

Stability | provisional |

Maintainer | John Goerzen <jgoerzen@complete.org> |

Safe Haskell | Safe-Inferred |

- boundedConversion :: (Ord a, Bounded b, Show a, Show b, Convertible a Integer, Convertible b Integer, Typeable a, Typeable b) => (a -> ConvertResult b) -> a -> ConvertResult b
- convertVia :: (Convertible a b, Convertible b c) => b -> a -> ConvertResult c

# Documentation

:: (Ord a, 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.

:: (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.