[Haskell-cafe] How does one create an input handle bound to a string instead of a file?

[John D. Ramsdell]

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 <ganesh at earth.li> 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
>
>