Hash in Haskell

Tue, 17 Jun 2003 13:13:59 +1000

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Stable names/references may be what you need.

http://research.microsoft.com/~simonpj/Papers/weak.htm

Cheers

-----Original Message-----
From: Sergio Sebasti=E1n Giro [mailto:sergio@fceia.unr.edu.ar]
Sent: Tuesday, 17 June, 2003 12:08 PM
To: gilesb@cpsc.ucalgary.ca
Cc: haskell@haskell.org
Subject: Re: Hash in Haskell

On Mon, 16 Jun 2003 gilesb@cpsc.ucalgary.ca wrote:
Thanks anyway, but I want to maintain a set of elements of some (fixed)
unknown type. In a hash table, I can see in O(1) aprox. if the element
belongs  or not to set.

> Typically, such functions are often used to implement mappings from
> something (such as a String) to something else.
>
> If that is what you want take a  look at the type FiniteMap under the
> Data area of GHC and HUGS. It implements all the needed functionality
> without having to worry about creating a Hash for the keys.
>
> If you want if for some other reason, you would typically need to =
define
> a class such as:
>
> Class Hash where
>    hash::a->Int
>
> and then implement it on your desired types. Strings are ususally
> somewhat easy to create a unique has value, other types will, =
naturally,
> depend on what is in them.
>
>
>
> On 16 Jun, Sergio Sebasti=E1n Giro wrote:
> > Hi, I need some function in Haskell to hash any value from any type =
to
> > Int. I guess that such a function needs to be a primitive, but I =
don't
> > found it in Hugs. Do you know how I can implement it or found it?
> > Thanks
> > Sergio
> > _______________________________________________
> > Haskell mailing list
> > Haskell@haskell.org
> > http://www.haskell.org/mailman/listinfo/haskell
>
> --
> Brett G. Giles
> Grad Student, University of Calgary
> Formal Methods, Category Theory, Semantics of Programming
> http://www.cpsc.ucalgary.ca/~gilesb     =
mailto:gilesb@cpsc.ucalgary.ca
>
>
_______________________________________________
Haskell mailing list
Haskell@haskell.org
http://www.haskell.org/mailman/listinfo/haskell

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<P><FONT SIZE=3D2>Stable names/references may be what you need.</FONT>
</P>

<P><FONT SIZE=3D2><A =
HREF=3D"http://research.microsoft.com/~simonpj/Papers/weak.htm" =
TARGET=3D"_blank">http://research.microsoft.com/~simonpj/Papers/weak.htm=
</A></FONT>
</P>

<P><FONT SIZE=3D2>Cheers</FONT>
</P>

<P><FONT SIZE=3D2>-----Original Message-----</FONT>
<BR><FONT SIZE=3D2>From: Sergio Sebasti=E1n Giro [<A =
HREF=3D"mailto:sergio@fceia.unr.edu.ar">mailto:sergio@fceia.unr.edu.ar</=
A>]</FONT>
<BR><FONT SIZE=3D2>Sent: Tuesday, 17 June, 2003 12:08 PM</FONT>
<BR><FONT SIZE=3D2>To: gilesb@cpsc.ucalgary.ca</FONT>
<BR><FONT SIZE=3D2>Cc: haskell@haskell.org</FONT>
<BR><FONT SIZE=3D2>Subject: Re: Hash in Haskell</FONT>
</P>
<BR>

On Mon, 16 Jun 2003 gilesb@cpsc.ucalgary.ca =
wrote:
 Thanks anyway, but I want to maintain a set of =
elements of some (fixed)
 unknown type. In a hash table, I can see in O(1) =
aprox. if the element
 belongs&nbsp; or not to set.

&gt; Typically, such functions are often used to =
implement mappings from
 &gt; something (such as a String) to something =
else.
 &gt;
 &gt; If that is what you want take a&nbsp; look at =
the type FiniteMap under the
 &gt; Data area of GHC and HUGS. It implements all =
the needed functionality
 &gt; without having to worry about creating a Hash =
for the keys.
 &gt;
 &gt; If you want if for some other reason, you would =
typically need to define
 &gt; a class such as:
 &gt;
 &gt; Class Hash where
 &gt;&nbsp;&nbsp;&nbsp; hash::a-&gt;Int
 &gt;
 &gt; and then implement it on your desired types. =
Strings are ususally
 &gt; somewhat easy to create a unique has value, =
other types will, naturally,
 &gt; depend on what is in them.
 &gt;
 &gt;
 &gt;
 &gt; On 16 Jun, Sergio Sebasti=E1n Giro =
wrote:
 &gt; &gt; Hi, I need some function in Haskell to =
hash any value from any type to
 &gt; &gt; Int. I guess that such a function needs to =
be a primitive, but I don't
 &gt; &gt; found it in Hugs. Do you know how I can =
implement it or found it?
 &gt; &gt; Thanks
 &gt; &gt; Sergio
 &gt; &gt; =
_______________________________________________
 &gt; &gt; Haskell mailing list
 &gt; &gt; Haskell@haskell.org
 &gt; &gt; <A =
HREF=3D"http://www.haskell.org/mailman/listinfo/haskell" =
TARGET=3D"_blank">http://www.haskell.org/mailman/listinfo/haskell</A></F=
ONT>
 &gt;
 &gt; --
 &gt; Brett G. Giles
 &gt; Grad Student, University of Calgary
 &gt; Formal Methods, Category Theory, Semantics of =
Programming
 &gt; <A HREF=3D"http://www.cpsc.ucalgary.ca/~gilesb" =
TARGET=3D"_blank">http://www.cpsc.ucalgary.ca/~gilesb</A>&nbsp;&nbsp;&nb=
sp;&nbsp; <A =
HREF=3D"mailto:gilesb@cpsc.ucalgary.ca">mailto:gilesb@cpsc.ucalgary.ca</=
A>
 &gt;
 &gt;
 _______________________________________________
 Haskell mailing list
 Haskell@haskell.org
 <A =
HREF=3D"http://www.haskell.org/mailman/listinfo/haskell" =
TARGET=3D"_blank">http://www.haskell.org/mailman/listinfo/haskell</A></F=
ONT>

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