How does one create an input handle bound to a string instead of a file?

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John D. Ramsdell

27 Feb 2013 27 Feb '13

3:38 p.m.

How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance. John

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Gregory Collins

27 Feb 27 Feb

5:50 p.m.

New subject: How does one create an input handle bound to a string instead of a file?

On Wed, Feb 27, 2013 at 9:38 PM, John D. Ramsdell wrote:

...

How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

You can't. There are several libraries that purport to provide better interfaces for doing IO in Haskell, like conduit, pipes, enumerator, and my own io-streams library (http://github.com/snapframework/io-streams, soon to be released). You could try one of those. G -- Gregory Collins

Don Stewart

6:15 p.m.

New subject: How does one create an input handle bound to a string instead of a file?

I don't think that's right - Simon's buffer class rewrite should have made this possible, I think. http://hackage.haskell.org/packages/archive/base/4.2.0.1/doc/html/GHC-IO-Buf... On Feb 27, 2013 10:52 PM, "Gregory Collins" wrote:

...

On Wed, Feb 27, 2013 at 9:38 PM, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

You can't. There are several libraries that purport to provide better interfaces for doing IO in Haskell, like conduit, pipes, enumerator, and my own io-streams library (http://github.com/snapframework/io-streams, soon to be released). You could try one of those.

G -- Gregory Collins

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Gregory Collins

6:23 p.m.

New subject: How does one create an input handle bound to a string instead of a file?

Hm, perhaps I stand corrected. Then how exactly do you make the bytestring Handle? On Thu, Feb 28, 2013 at 12:15 AM, Don Stewart wrote:

...

I don't think that's right - Simon's buffer class rewrite should have made this possible, I think.

http://hackage.haskell.org/packages/archive/base/4.2.0.1/doc/html/GHC-IO-Buf... On Feb 27, 2013 10:52 PM, "Gregory Collins" wrote:

...
On Wed, Feb 27, 2013 at 9:38 PM, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

You can't. There are several libraries that purport to provide better interfaces for doing IO in Haskell, like conduit, pipes, enumerator, and my own io-streams library (http://github.com/snapframework/io-streams, soon to be released). You could try one of those.

G -- Gregory Collins

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-- Gregory Collins

Bob Ippolito

10:05 p.m.

New subject: How does one create an input handle bound to a string instead of a file?

I haven't had time to make an example yet but it looks like if you go down to GHC.IO.Handle.Internals there's a mkHandle function that takes a BufferedIO and some other stuff and gives you an IO Handle. On Wed, Feb 27, 2013 at 3:23 PM, Gregory Collins wrote:

...

Hm, perhaps I stand corrected. Then how exactly do you make the bytestring Handle?

On Thu, Feb 28, 2013 at 12:15 AM, Don Stewart wrote:

...
I don't think that's right - Simon's buffer class rewrite should have made this possible, I think.

http://hackage.haskell.org/packages/archive/base/4.2.0.1/doc/html/GHC-IO-Buf... On Feb 27, 2013 10:52 PM, "Gregory Collins" wrote:

...
On Wed, Feb 27, 2013 at 9:38 PM, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

You can't. There are several libraries that purport to provide better interfaces for doing IO in Haskell, like conduit, pipes, enumerator, and my own io-streams library (http://github.com/snapframework/io-streams, soon to be released). You could try one of those.

G -- Gregory Collins

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

-- Gregory Collins

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

John D. Ramsdell

28 Feb 28 Feb

8:42 a.m.

New subject: How does one create an input handle bound to a string instead of a file?

I couldn't find the mkHandle function in the source linked to the specified Haddock generated documentation page. If there is a consensus that others besides myself would like a function with the signature stringHandle :: String -> IO (Handle) I'd be happy to contribute code. I'd need help as I haven't ever contributed this kind of code. John On Wed, Feb 27, 2013 at 10:05 PM, Bob Ippolito wrote:

...

I haven't had time to make an example yet but it looks like if you go down to GHC.IO.Handle.Internals there's a mkHandle function that takes a BufferedIO and some other stuff and gives you an IO Handle.

On Wed, Feb 27, 2013 at 3:23 PM, Gregory Collins wrote:

...
Hm, perhaps I stand corrected. Then how exactly do you make the bytestring Handle?

On Thu, Feb 28, 2013 at 12:15 AM, Don Stewart wrote:

...
I don't think that's right - Simon's buffer class rewrite should have made this possible, I think.

http://hackage.haskell.org/packages/archive/base/4.2.0.1/doc/html/GHC-IO-Buf...

On Feb 27, 2013 10:52 PM, "Gregory Collins" wrote:

...
On Wed, Feb 27, 2013 at 9:38 PM, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

You can't. There are several libraries that purport to provide better interfaces for doing IO in Haskell, like conduit, pipes, enumerator, and my own io-streams library (http://github.com/snapframework/io-streams, soon to be released). You could try one of those.

G -- Gregory Collins

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

-- Gregory Collins

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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Ganesh Sittampalam

3:02 a.m.

New subject: How does one create an input handle bound to a string instead of a file?

Hi, On 27/02/2013 20:38, John D. Ramsdell wrote:

...

How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

http://hackage.haskell.org/package/bytestring-handle can make handles that read and write to ByteStrings. Cheers, Ganesh

John D. Ramsdell

8:32 a.m.

New subject: How does one create an input handle bound to a string instead of a file?

I think I wasn't clear about my question. I want something that creates a value of type System.IO.Handle. You see, I have a high performance S-expression parser that I'd like to use in GHCi reading strings while at the command loop. Here is more details on my module SExpr that exports the SExpr data type and the load function. The desired function is called stringHandle. -- An S-expression data SExpr = S String -- A symbol | Q String -- A quoted string | N Int -- An integer | L [SExpr a] -- A proper list -- Read one S-expression or return Nothing on EOF load :: Handle -> IO (Maybe (SExpr Pos)) In GHCi, I want to type something like: SExpr> let h = stringHandle "()" SExpr> load h Just (L []) SExpr> load h Nothing SExpr> It seems to me right now that I have to implement a duplicate parser that implements Read. At least S-expression parsing is easy. John On Thu, Feb 28, 2013 at 3:02 AM, Ganesh Sittampalam wrote:

...

Hi,

On 27/02/2013 20:38, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

http://hackage.haskell.org/package/bytestring-handle can make handles that read and write to ByteStrings.

Cheers,

Ganesh

Ganesh Sittampalam

8:40 a.m.

New subject: How does one create an input handle bound to a string instead of a file?

Hi John, Using bytestring-handle, you can get this with something like stringHandle :: String -> Handle stringHandle s = readHandle False (Data.ByteString.Char8.pack s) [note the complete disregard of encoding issues in the use of Data.ByteString.Char8] Cheers, Ganesh On 28/02/2013 13:32, John D. Ramsdell wrote:

...

I think I wasn't clear about my question. I want something that creates a value of type System.IO.Handle. You see, I have a high performance S-expression parser that I'd like to use in GHCi reading strings while at the command loop.

Here is more details on my module SExpr that exports the SExpr data type and the load function. The desired function is called stringHandle.

-- An S-expression data SExpr = S String -- A symbol | Q String -- A quoted string | N Int -- An integer | L [SExpr a] -- A proper list

-- Read one S-expression or return Nothing on EOF load :: Handle -> IO (Maybe (SExpr Pos))

In GHCi, I want to type something like:

SExpr> let h = stringHandle "()" SExpr> load h Just (L []) SExpr> load h Nothing SExpr>

It seems to me right now that I have to implement a duplicate parser that implements Read. At least S-expression parsing is easy.

John

On Thu, Feb 28, 2013 at 3:02 AM, Ganesh Sittampalam wrote:

...
Hi,

On 27/02/2013 20:38, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

http://hackage.haskell.org/package/bytestring-handle can make handles that read and write to ByteStrings.

Cheers,

Ganesh

John D. Ramsdell

8:49 a.m.

New subject: How does one create an input handle bound to a string instead of a file?

I see now. I read the source code incorrectly. Now I know what to do. John On Thu, Feb 28, 2013 at 8:40 AM, Ganesh Sittampalam wrote:

...

Hi John,

Using bytestring-handle, you can get this with something like

stringHandle :: String -> Handle stringHandle s = readHandle False (Data.ByteString.Char8.pack s)

[note the complete disregard of encoding issues in the use of Data.ByteString.Char8]

Cheers,

Ganesh

On 28/02/2013 13:32, John D. Ramsdell wrote:

...
I think I wasn't clear about my question. I want something that creates a value of type System.IO.Handle. You see, I have a high performance S-expression parser that I'd like to use in GHCi reading strings while at the command loop.

Here is more details on my module SExpr that exports the SExpr data type and the load function. The desired function is called stringHandle.

-- An S-expression data SExpr = S String -- A symbol | Q String -- A quoted string | N Int -- An integer | L [SExpr a] -- A proper list

-- Read one S-expression or return Nothing on EOF load :: Handle -> IO (Maybe (SExpr Pos))

In GHCi, I want to type something like:

SExpr> let h = stringHandle "()" SExpr> load h Just (L []) SExpr> load h Nothing SExpr>

It seems to me right now that I have to implement a duplicate parser that implements Read. At least S-expression parsing is easy.

John

On Thu, Feb 28, 2013 at 3:02 AM, Ganesh Sittampalam wrote:

...
Hi,

On 27/02/2013 20:38, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

http://hackage.haskell.org/package/bytestring-handle can make handles that read and write to ByteStrings.

Cheers,

Ganesh

Erik Hesselink

9 a.m.

New subject: How does one create an input handle bound to a string instead of a file?

Is your parser impure? I would expect a function from String/Text/ByteString to Maybe (SExpr Pos). Then you have no need for a Handle. Regards, Erik On Thu, Feb 28, 2013 at 2:32 PM, John D. Ramsdell wrote:

...

I think I wasn't clear about my question. I want something that creates a value of type System.IO.Handle. You see, I have a high performance S-expression parser that I'd like to use in GHCi reading strings while at the command loop.

Here is more details on my module SExpr that exports the SExpr data type and the load function. The desired function is called stringHandle.

-- An S-expression data SExpr = S String -- A symbol | Q String -- A quoted string | N Int -- An integer | L [SExpr a] -- A proper list

-- Read one S-expression or return Nothing on EOF load :: Handle -> IO (Maybe (SExpr Pos))

In GHCi, I want to type something like:

SExpr> let h = stringHandle "()" SExpr> load h Just (L []) SExpr> load h Nothing SExpr>

It seems to me right now that I have to implement a duplicate parser that implements Read. At least S-expression parsing is easy.

John

On Thu, Feb 28, 2013 at 3:02 AM, Ganesh Sittampalam wrote:

...
Hi,

On 27/02/2013 20:38, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

http://hackage.haskell.org/package/bytestring-handle can make handles that read and write to ByteStrings.

Cheers,

Ganesh

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

John D. Ramsdell

10:10 a.m.

New subject: How does one create an input handle bound to a string instead of a file?

The actual parser is a bit more complicated than I let on. First, it's important that not all of a file be read at the same time as the files can be huge. Second, it keeps track of column row position information as an IORef, which makes sense because the ref is bundled in a structure with the handle and manipulated only in the IO Monad in conjunction with operations on the handle. John On Thu, Feb 28, 2013 at 9:00 AM, Erik Hesselink wrote:

...

Is your parser impure? I would expect a function from String/Text/ByteString to Maybe (SExpr Pos). Then you have no need for a Handle.

Regards,

Erik

On Thu, Feb 28, 2013 at 2:32 PM, John D. Ramsdell wrote:

...
I think I wasn't clear about my question. I want something that creates a value of type System.IO.Handle. You see, I have a high performance S-expression parser that I'd like to use in GHCi reading strings while at the command loop.

Here is more details on my module SExpr that exports the SExpr data type and the load function. The desired function is called stringHandle.

-- An S-expression data SExpr = S String -- A symbol | Q String -- A quoted string | N Int -- An integer | L [SExpr a] -- A proper list

-- Read one S-expression or return Nothing on EOF load :: Handle -> IO (Maybe (SExpr Pos))

In GHCi, I want to type something like:

SExpr> let h = stringHandle "()" SExpr> load h Just (L []) SExpr> load h Nothing SExpr>

It seems to me right now that I have to implement a duplicate parser that implements Read. At least S-expression parsing is easy.

John

On Thu, Feb 28, 2013 at 3:02 AM, Ganesh Sittampalam wrote:

...
Hi,

On 27/02/2013 20:38, John D. Ramsdell wrote:

...
How does one create a value of type System.IO.Handle for reading that takes its input from a string instead of a file? I'm looking for the equivalent of java.io.StringReader in Java. Thanks in advance.

http://hackage.haskell.org/package/bytestring-handle can make handles that read and write to ByteStrings.

Cheers,

Ganesh

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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participants (6)

Bob Ippolito
Don Stewart
Erik Hesselink
Ganesh Sittampalam
Gregory Collins
John D. Ramsdell