#3676: realToFrac doesn't sanely convert between floating types
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Reporter: draconx | Owner: simonmar
Type: bug | Status: assigned
Priority: normal | Milestone: 6.12.2
Component: libraries (other) | Version: 6.12.1
Keywords: | Difficulty:
Os: Unknown/Multiple | Testcase:
Architecture: x86_64 (amd64) | Failure: None/Unknown
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Comment(by draconx):
The problem with non-overloaded functions is that there are a lot of them:
12 with the four floating types that currently exist, and 30 if long
double is ever added (two types: LDouble & CLDouble). This problem could
be mitigated by only providing the trivial conversions when FFI types are
involved: that is, provide Double <=> CDouble, but don't bother with Float
<=> CDouble.
On the other hand, we could use a single parameter version of altfloat's
technique as follows:
{{{
class FloatConvert a where
toDouble :: a -> Double
}}}
since Double can represent all values of every other floating type (at
least until long double exists). Then we could have a `fromDouble` member
in the RealFloat class, and define `toFloating = fromDouble . toDouble`
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3676#comment:13>
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