I will surely take a look. Bertram Felgenhauer has come up with a nice improvement to the Integer building algorithm; I don't know if you have something better. Fractional stuff indeed looks very tricky; the current code, however, seems unlikely to be taking the right approach.
I totally agree that the desired semantics should be:
> readsInt "12e-3" = [12,"e-3"] -- yes, there is an int at the beginning of the string.
> readsInt ('a' : ...) = [] -- yes, we can tell there isn't an int at the beginning of the string.
In terms of algorithms for parsing things efficiently as well as
failing fast, I highly recommend looking at what bytestring-lexing
does. Though the implementations there read in ByteStrings, there's
nothing about the algorithms that depends on that representation.
Getting efficient (and correct!) parsing for Fractional types is quite
a lot more complicated than it looks on the surface.
--
Live well,
~wren
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