Adding String interface?

[Icelandjack]

This may be controversial (“String incompatible (probably a plus)”) but I think it's worth discussing.

String is still in use and it would be nice to be able to use the library without OverloadedStrings, many beginners avoid language extensions and the error messages from overloading strings can be daunting so adding an option for String may lower the barrier to entry. Currently Text.Printf.printf works with strings so formatting can't be used as a drop-in replacement.

Since overloaded strings are used to interpret Holey as a string I see three ways:

• One solution would be to only provide a function that unpacks the final text (so OverloadedStrings would still be required).
• Or a function with a short name could be used to prefix strings r"..." serving as a conversion function to Holey, I haven't tried this but I don't think the extensions is needed for that.
• Leave it as it is.

To discourage String usage by default it can be put in Formatting.String.

[Icelandjack]

Here's an example from the second idea without using OverloadedStrings, it's of course messier but that may serve as an encouragement to switch to Text :)

ghci> :set -XNoOverloadedStrings 
ghci> import Data.String
ghci> let r = fromString
ghci> format (r"hi-" % int % r"!") 5
"hi-5!"

[chrisdone]

I'm not quite sure exactly what this issue is addressing. Is it only against the OverloadedStrings extension?

[Icelandjack]

The issue is mainly about also having a formatting function that returns the more familiar String without having to unpack it manually, the function definition is simple enough and can be used with and without OverloadedStrings:

strFormat :: Holey Builder String a -> a
strFormat m = runHM m (T.unpack . T.toLazyText)

And so can the normal format:

ghci> let r = fromString 
ghci> strFormat (r"Name: "%s%r", age: "%int) "Emma" 24
"Name: Emma, age: 24"
it :: String
ghci> format (r"Name: "%s%r", age: "%int) "Emma" 24
"Name: Emma, age: 24"
it :: Text
ghci> :set -XOverloadedStrings
ghci> take 5 (strFormat ("Name: "%s%", age: "%int) "Emma" 24)
"Name:"
it :: [Char]

So adding strFormat is fairly orthogonal to OverloadedStrings.

[chrisdone]

This is fine. I'm not sure I want to cater to people using String preemptively… maybe if some newbie asks for it. Right now this seems hypothetical only. =)

[Icelandjack]

Fair enough. I thought it was a bigger change initially but avoiding OverloadedStrings can be done with a single definition … = fromString and strFormat is easy enough to define. It would be nice to give people fewer excuses to use the not-so-type-safe printf :) I'll close it