I am curious to understand the logic, the "Haskell Think", here. Why is it that the byteString only supports conversion to int. daryoush On Sun, Aug 24, 2008 at 2:23 PM, Don Stewart wrote:

dmehrtash:

...

I am trying to convert a string to a float. It seems that Data.ByteString library only supports readInt. After some googling I came accross a possibloe implementation: [1]http://sequence.svcs.cs.pdx.edu/node/373

Use the bytstring-lexing library,

http://hackage.haskell.org/cgi-bin/hackage-scripts/package/bytestring-lexing

Which provides a copying and non-copying lexer for doubles,

readDouble :: ByteString -> Maybe (Double, ByteString) unsafeReadDouble :: ByteString -> Maybe (Double, ByteString)

-- Don

Because normally, Prelude.read covers this. Don's link is the most efficient, but you can also do (read . ByteString.unpack $ bytestring) :: Double to get a Double from a printed representation of most numbers. 2008/8/24 Daryoush Mehrtash :

I am curious to understand the logic, the "Haskell Think", here. Why is it that the byteString only supports conversion to int.

daryoush On Sun, Aug 24, 2008 at 2:23 PM, Don Stewart wrote:

...

dmehrtash:

...

I am trying to convert a string to a float. It seems that Data.ByteString library only supports readInt. After some googling I came accross a possibloe implementation: [1]http://sequence.svcs.cs.pdx.edu/node/373

Use the bytstring-lexing library,

http://hackage.haskell.org/cgi-bin/hackage-scripts/package/bytestring-lexing

Which provides a copying and non-copying lexer for doubles,

readDouble :: ByteString -> Maybe (Double, ByteString) unsafeReadDouble :: ByteString -> Maybe (Double, ByteString)

-- Don

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Bjorn, I am initializing a list from a file. I am reading the lines from the file, splitting them into bytestring and then converting them to float. Should I be using String -> Float or ByteString -> Float? thanks Daryoush On Tue, Aug 26, 2008 at 6:01 AM, Bjorn Bringert wrote:

2008/8/24 Daryoush Mehrtash :

...

I am trying to convert a string to a float. It seems that Data.ByteString library only supports readInt. After some googling I came accross a possibloe implementation: http://sequence.svcs.cs.pdx.edu/node/373

My questions are:

a) is there a standard library implementation of string -> Double and float? b) Why is it that the ByteString only supports readInt? Is there a reason for it?

Hi Daryoush,

are you really looking for ByteString -> Float conversion, or just plain String -> Float? The latter is really simple, the function is called 'read' and is available in the Prelude:

$ ghci GHCi, version 6.8.3: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude> read "3.14" :: Float 3.14

/Bjorn

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