Number to Text conversion

[dschrempf]

Hi,

may I suggest adding conversion functions such as

import qualified Data.Text as T
import qualified Data.Text.Lazy as T (toStrict)
import qualified Data.Text.Lazy.Builder as B
import qualified Data.Text.Lazy.Builder.Int as B
import qualified Data.Text.Lazy.Builder.RealFloat as B

realFloatToText :: RealFloat a => a -> T.Text
realFloatToText = T.toStrict . B.toLazyText . B.realFloat

intToText :: Integral a => a -> T.Text
intToText = T.toStrict . B.toLazyText . B.decimal

to Data.Text because I spent now around two hours in finding a way to convert numbers to Text objects. Maybe there is a better way, in that case it would be nice to have it documented in the main file of the module.

Thank you!

[Fuuzetsu]

http://hackage.haskell.org/package/double-conversion-2.0.2.0 ?

[robwithhair]

+1 very confusing not having the fastest solution as part of the Text package. Please consider adding or directing readers of documentation in the right direction.

[Anton-Latukha]

Agree.

I think there is no debate there should be a fast function to convert: Integral a => a -> Text at least.
Very surprised the fastest ways in the default library are manually through Lazy Builder, then assemble it, then additionally run O(n) toStrict on it, it is, well, a bit excessive.

There is: text-builder where is decimal :: Integral a => a -> Builder.
Good if that package would've been upstreamed here.

[jkaye2012]

Is this request under consideration? I was surprised to find that this does not exist yet.

[Bodigrim]

Float-to-string conversion is hard. Once haskell/bytestring#365 lands into bytestring and UTF8-based text-2.0 is released, the fastest way will be to create a ByteString and convert it to Text.

[BebeSparkelSparkel]

@Bodigrim Currently, the haskell/bytestring#365 has been pulled but, I have recently updated the float to string implementation in bytestring and have greatly improved its performance and added some capabilities. However, I have not made any breaking changes to the interface and integration to text can begin now.

The performance and organization PRs currently submitted

• Overhaul realfloat bytestring#637
• Better Tests and Benchmarks for Float and Double Builders bytestring#638
• Quick Optimization for showStandard bytestring#639

New formatting options

• Padded exponent bytestring#644
• Explicit exponent sign bytestring#646

Also, the Ryu algorithm may not print floating point numbers the same as your current implementation since it minimizes the the number of digits printed. I have not looked at the text implementation so this may not be an issue.

[Bodigrim]

Thanks @BebeSparkelSparkel. I'm severely overloaded at the moment, but I'm sure @clyring will review your PRs for bytestring. Feel free to ping me in a couple of weeks though.

A PR migrating text to use bytestring for double-to-string conversion would be welcome.

[Bodigrim]

I think it's time we add

intToText :: Integral a => a -> T.Text
intToText = T.toStrict . B.toLazyText . B.decimal

because this incantation is so arcane that the vast majority of users succumb to T.pack . show, which is very inefficient.

I'm unsure about the name. It should mention that it's a decimal representation, not hexadecimal. Maybe simply Data.Text.decimal?..