Fractional instances for Sum, Product
Should Data.Monoid.Sum
and Product
have Fractional
instances? The current situation means
> 10 <> 20 :: Sum Double
Sum {getSum = 30.0}
compiles but fails with fractional numeric literal
> 10.5 <> 20 :: Sum Double
<interactive>:8:1: error:
• No instance for (Fractional (Sum Double))
arising from the literal ‘10.5’
• In the first argument of ‘(<>)’, namely ‘10.5’
In the expression: 10.5 <> 20 :: Sum Double
In an equation for ‘it’: it = 10.5 <> 20 :: Sum Double