[Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
Hello,
I'm trying to find out if it's possible to use Haskell data type
definition capability to define types and compile defined types into
other languages, for example into Google's protocol buffers data
definition language. So basically speaking I'm thinking about using
Haskell sub-set as a data-definition DSL together with some functions
which will generate some code based on supplied defined data types. My
idea is:
data Person = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
emit_proto Person 1
where emit_proto is function which will translate Person data type
definition into Google's proto language (the 1 is index from which start
to index type's fields) by traversing data type definition and
translating all its children plus do some header/footer generation etc:
message Person {
required int32 id = 1;
required string name = 2;
optional string email = 3;
}
I've looked for something like that and found SYB papers which works on
top of data instance (i.e. actual data, not data type). I also found
JSON lib which again works on top of data and not data type. I've tried
to look into Data.Typetable etc, but have not found function which will
print data type's field name and field type name (although JSON lib
seems to use field name for JSON generation so I'll need to investigate
this more). I've tested `typeOf' function and it's quite useful, but its
limitation is that it's not working on ADT name:
data Color = RED|GREEN|BLUE
*Main typeOf Color
interactive:1:8: Not in scope: data constructor `Color'
*Main typeOf RED
Main.Color
and I would need that in order to translate Color defined above into
enum like:
enum Color {
RED = 0;
GREEN = 1;
BLUE = 2;
}
My question is: do you think I'm looking into good direction (i.e.
Data/Typeable) or do you think I'll need to use something different for
data definition DSL (Template Haskell?, or impossible in Haskell so
write my own language with full parser? etc?)
Thanks for any idea or opinion on this!
Karel
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Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
Just making sure: have you looked at the Data.Data module yet?
Edward
Excerpts from Karel Gardas's message of Tue Oct 04 12:02:34 -0400 2011:
Hello,
I'm trying to find out if it's possible to use Haskell data type
definition capability to define types and compile defined types into
other languages, for example into Google's protocol buffers data
definition language. So basically speaking I'm thinking about using
Haskell sub-set as a data-definition DSL together with some functions
which will generate some code based on supplied defined data types. My
idea is:
data Person = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
emit_proto Person 1
where emit_proto is function which will translate Person data type
definition into Google's proto language (the 1 is index from which start
to index type's fields) by traversing data type definition and
translating all its children plus do some header/footer generation etc:
message Person {
required int32 id = 1;
required string name = 2;
optional string email = 3;
}
I've looked for something like that and found SYB papers which works on
top of data instance (i.e. actual data, not data type). I also found
JSON lib which again works on top of data and not data type. I've tried
to look into Data.Typetable etc, but have not found function which will
print data type's field name and field type name (although JSON lib
seems to use field name for JSON generation so I'll need to investigate
this more). I've tested `typeOf' function and it's quite useful, but its
limitation is that it's not working on ADT name:
data Color = RED|GREEN|BLUE
*Main typeOf Color
interactive:1:8: Not in scope: data constructor `Color'
*Main typeOf RED
Main.Color
and I would need that in order to translate Color defined above into
enum like:
enum Color {
RED = 0;
GREEN = 1;
BLUE = 2;
}
My question is: do you think I'm looking into good direction (i.e.
Data/Typeable) or do you think I'll need to use something different for
data definition DSL (Template Haskell?, or impossible in Haskell so
write my own language with full parser? etc?)
Thanks for any idea or opinion on this!
Karel
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Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
Hi Karel,
You can use SYB's toConstr/dataTypeOf [1] to obtain information about the
name of the constructor and datatype. Alternatively, you can also use the
new generic programming framework of ghc-7.2 [2].
Cheers,
Pedro
[1]
http://hackage.haskell.org/packages/archive/base/latest/doc/html/Data-Data.html#v:toConstr
[2]
http://haskell.org/ghc/docs/latest/html/libraries/ghc-prim-0.2.0.0/GHC-Generics.html#t:Datatype
On Tue, Oct 4, 2011 at 17:02, Karel Gardas karel.gar...@centrum.cz wrote:
Hello,
I'm trying to find out if it's possible to use Haskell data type definition
capability to define types and compile defined types into other languages,
for example into Google's protocol buffers data definition language. So
basically speaking I'm thinking about using Haskell sub-set as a
data-definition DSL together with some functions which will generate some
code based on supplied defined data types. My idea is:
data Person = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
emit_proto Person 1
where emit_proto is function which will translate Person data type
definition into Google's proto language (the 1 is index from which start to
index type's fields) by traversing data type definition and translating all
its children plus do some header/footer generation etc:
message Person {
required int32 id = 1;
required string name = 2;
optional string email = 3;
}
I've looked for something like that and found SYB papers which works on top
of data instance (i.e. actual data, not data type). I also found JSON lib
which again works on top of data and not data type. I've tried to look into
Data.Typetable etc, but have not found function which will print data type's
field name and field type name (although JSON lib seems to use field name
for JSON generation so I'll need to investigate this more). I've tested
`typeOf' function and it's quite useful, but its limitation is that it's not
working on ADT name:
data Color = RED|GREEN|BLUE
*Main typeOf Color
interactive:1:8: Not in scope: data constructor `Color'
*Main typeOf RED
Main.Color
and I would need that in order to translate Color defined above into enum
like:
enum Color {
RED = 0;
GREEN = 1;
BLUE = 2;
}
My question is: do you think I'm looking into good direction (i.e.
Data/Typeable) or do you think I'll need to use something different for data
definition DSL (Template Haskell?, or impossible in Haskell so write my own
language with full parser? etc?)
Thanks for any idea or opinion on this!
Karel
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Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
An interesting and semi-related project was just presented at ICFP by
Kathleen Fisher. It's called Forest and uses template haskell to create
schema's for FileStores from Haskell definitions. But they're not
plain-old-haskell type definitions...
-Ryan
On Tue, Oct 4, 2011 at 12:11 PM, Edward Z. Yang ezy...@mit.edu wrote:
Just making sure: have you looked at the Data.Data module yet?
Edward
Excerpts from Karel Gardas's message of Tue Oct 04 12:02:34 -0400 2011:
Hello,
I'm trying to find out if it's possible to use Haskell data type
definition capability to define types and compile defined types into
other languages, for example into Google's protocol buffers data
definition language. So basically speaking I'm thinking about using
Haskell sub-set as a data-definition DSL together with some functions
which will generate some code based on supplied defined data types. My
idea is:
data Person = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
emit_proto Person 1
where emit_proto is function which will translate Person data type
definition into Google's proto language (the 1 is index from which start
to index type's fields) by traversing data type definition and
translating all its children plus do some header/footer generation etc:
message Person {
required int32 id = 1;
required string name = 2;
optional string email = 3;
}
I've looked for something like that and found SYB papers which works on
top of data instance (i.e. actual data, not data type). I also found
JSON lib which again works on top of data and not data type. I've tried
to look into Data.Typetable etc, but have not found function which will
print data type's field name and field type name (although JSON lib
seems to use field name for JSON generation so I'll need to investigate
this more). I've tested `typeOf' function and it's quite useful, but its
limitation is that it's not working on ADT name:
data Color = RED|GREEN|BLUE
*Main typeOf Color
interactive:1:8: Not in scope: data constructor `Color'
*Main typeOf RED
Main.Color
and I would need that in order to translate Color defined above into
enum like:
enum Color {
RED = 0;
GREEN = 1;
BLUE = 2;
}
My question is: do you think I'm looking into good direction (i.e.
Data/Typeable) or do you think I'll need to use something different for
data definition DSL (Template Haskell?, or impossible in Haskell so
write my own language with full parser? etc?)
Thanks for any idea or opinion on this!
Karel
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Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
On 4 October 2011 17:02, Karel Gardas karel.gar...@centrum.cz wrote: Hello, [SNIP] So basically speaking I'm thinking about using Haskell sub-set as a data-definition DSL together with some functions which will generate some code based on supplied defined data types. ... This seems reminiscent of ASDL - the Abstract Syntax Definition Language - and ASDLgen (its generator) which used sum and product types (essentially the same a Haskell or ML's algebraic types) to define data for compiler internals. The definitions could be compiled to C++, C, Java, ML, and Haskell. As well as data type definitions ASDLgen generated marshallers for the ASDL binary format. Unfortunately the Zephyr project which sponsored ASDL seems to have had an early demise - so what info there still is available on the web might be patchy. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
Hello,
thanks a lot to Edward, Jose, Ryan and Stephen for fast reply in this
thread. I see I've not been that precise in specification of what I need
exactly so I need to add this: I've changed a little bit definition of
person to:
data PersonType = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
so I have `PersonType' as type constructor and Person as value
constructor (or data constructor) -- speaking using terms from Real
World Haskell, Chapter 3[1]. And now I see that none of
typeOf/dataTypeOf/toContr is applicable to *type constructor* but all
are applicable to *value/data constructor*. Ditto happen when testing
Color versus RED, GREEN, BLUE. At least GHCi complains this way:
*Main typeOf Color
interactive:0:8: Not in scope: data constructor `Color'
*Main typeOf PersonType
interactive:0:8: Not in scope: data constructor `PersonType'
But, I'd like to start processing of data definition from the *type
constructor*. So:
emit_proto PersonType 1
emit_proto Color 1
Is that possible at all? I mean in the scope/context of GHC's
Data/Data.Data/Data.Typeable etc. modules. (w/o considering TH now).
Thanks!
Karel
[1]:
http://book.realworldhaskell.org/read/defining-types-streamlining-functions.html
On 10/ 4/11 06:02 PM, Karel Gardas wrote:
Hello,
I'm trying to find out if it's possible to use Haskell data type
definition capability to define types and compile defined types into
other languages, for example into Google's protocol buffers data
definition language. So basically speaking I'm thinking about using
Haskell sub-set as a data-definition DSL together with some functions
which will generate some code based on supplied defined data types. My
idea is:
data Person = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
emit_proto Person 1
where emit_proto is function which will translate Person data type
definition into Google's proto language (the 1 is index from which start
to index type's fields) by traversing data type definition and
translating all its children plus do some header/footer generation etc:
message Person {
required int32 id = 1;
required string name = 2;
optional string email = 3;
}
I've looked for something like that and found SYB papers which works on
top of data instance (i.e. actual data, not data type). I also found
JSON lib which again works on top of data and not data type. I've tried
to look into Data.Typetable etc, but have not found function which will
print data type's field name and field type name (although JSON lib
seems to use field name for JSON generation so I'll need to investigate
this more). I've tested `typeOf' function and it's quite useful, but its
limitation is that it's not working on ADT name:
data Color = RED|GREEN|BLUE
*Main typeOf Color
interactive:1:8: Not in scope: data constructor `Color'
*Main typeOf RED
Main.Color
and I would need that in order to translate Color defined above into
enum like:
enum Color {
RED = 0;
GREEN = 1;
BLUE = 2;
}
My question is: do you think I'm looking into good direction (i.e.
Data/Typeable) or do you think I'll need to use something different for
data definition DSL (Template Haskell?, or impossible in Haskell so
write my own language with full parser? etc?)
Thanks for any idea or opinion on this!
Karel
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Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
Forgotten note: GHC's Generics as described here:
http://haskell.org/ghc/docs/latest/html/libraries/ghc-prim-0.2.0.0/GHC-Generics.html#t:Datatype
-- is not yet clear to me, I'm searching for more information about this
in the meantime...
Karel
On 10/ 4/11 08:33 PM, Karel Gardas wrote:
Hello,
thanks a lot to Edward, Jose, Ryan and Stephen for fast reply in this
thread. I see I've not been that precise in specification of what I need
exactly so I need to add this: I've changed a little bit definition of
person to:
data PersonType = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
so I have `PersonType' as type constructor and Person as value
constructor (or data constructor) -- speaking using terms from Real
World Haskell, Chapter 3[1]. And now I see that none of
typeOf/dataTypeOf/toContr is applicable to *type constructor* but all
are applicable to *value/data constructor*. Ditto happen when testing
Color versus RED, GREEN, BLUE. At least GHCi complains this way:
*Main typeOf Color
interactive:0:8: Not in scope: data constructor `Color'
*Main typeOf PersonType
interactive:0:8: Not in scope: data constructor `PersonType'
But, I'd like to start processing of data definition from the *type
constructor*. So:
emit_proto PersonType 1
emit_proto Color 1
Is that possible at all? I mean in the scope/context of GHC's
Data/Data.Data/Data.Typeable etc. modules. (w/o considering TH now).
Thanks!
Karel
[1]:
http://book.realworldhaskell.org/read/defining-types-streamlining-functions.html
On 10/ 4/11 06:02 PM, Karel Gardas wrote:
Hello,
I'm trying to find out if it's possible to use Haskell data type
definition capability to define types and compile defined types into
other languages, for example into Google's protocol buffers data
definition language. So basically speaking I'm thinking about using
Haskell sub-set as a data-definition DSL together with some functions
which will generate some code based on supplied defined data types. My
idea is:
data Person = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
emit_proto Person 1
where emit_proto is function which will translate Person data type
definition into Google's proto language (the 1 is index from which start
to index type's fields) by traversing data type definition and
translating all its children plus do some header/footer generation etc:
message Person {
required int32 id = 1;
required string name = 2;
optional string email = 3;
}
I've looked for something like that and found SYB papers which works on
top of data instance (i.e. actual data, not data type). I also found
JSON lib which again works on top of data and not data type. I've tried
to look into Data.Typetable etc, but have not found function which will
print data type's field name and field type name (although JSON lib
seems to use field name for JSON generation so I'll need to investigate
this more). I've tested `typeOf' function and it's quite useful, but its
limitation is that it's not working on ADT name:
data Color = RED|GREEN|BLUE
*Main typeOf Color
interactive:1:8: Not in scope: data constructor `Color'
*Main typeOf RED
Main.Color
and I would need that in order to translate Color defined above into
enum like:
enum Color {
RED = 0;
GREEN = 1;
BLUE = 2;
}
My question is: do you think I'm looking into good direction (i.e.
Data/Typeable) or do you think I'll need to use something different for
data definition DSL (Template Haskell?, or impossible in Haskell so
write my own language with full parser? etc?)
Thanks for any idea or opinion on this!
Karel
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Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
On Tue, Oct 4, 2011 at 1:33 PM, Karel Gardas karel.gar...@centrum.cz wrote:
Hello,
thanks a lot to Edward, Jose, Ryan and Stephen for fast reply in this
thread. I see I've not been that precise in specification of what I need
exactly so I need to add this: I've changed a little bit definition of
person to:
data PersonType = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
so I have `PersonType' as type constructor and Person as value constructor
(or data constructor) -- speaking using terms from Real World Haskell,
Chapter 3[1]. And now I see that none of typeOf/dataTypeOf/toContr is
applicable to *type constructor* but all are applicable to *value/data
constructor*. Ditto happen when testing Color versus RED, GREEN, BLUE. At
least GHCi complains this way:
*Main typeOf Color
interactive:0:8: Not in scope: data constructor `Color'
*Main typeOf PersonType
interactive:0:8: Not in scope: data constructor `PersonType'
But, I'd like to start processing of data definition from the *type
constructor*. So:
emit_proto PersonType 1
emit_proto Color 1
You could use Data.Proxy and pass a type proxy as the first argument:
emit_proto (Proxy :: Proxy MyType) 1
It seems like you could then do something like `dataTypeOf
(asProxyTypeOf undefined proxy)` to unpack the 'Data' instance of the
proxied type. There might be a better way, but this is just what I can
think of off the top of my head.
The 'Poxy' type is here:
http://hackage.haskell.org/packages/archive/tagged/0.2.3.1/doc/html/Data-Proxy.html
Antoine
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Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
On Tue, Oct 4, 2011 at 20:33, Karel Gardas karel.gar...@centrum.cz wrote:
data PersonType = Person {
id :: Int
, name :: String
, email :: Maybe String
}
deriving (Show, Data, Typeable)
so I have `PersonType' as type constructor and Person as value constructor
(or data constructor) -- speaking using terms from Real World Haskell,
Chapter 3[1]. And now I see that none of typeOf/dataTypeOf/toContr is
applicable to *type constructor* but all are applicable to *value/data
constructor*. Ditto happen when testing Color versus RED, GREEN, BLUE. At
least GHCi complains this way:
*Main typeOf Color
interactive:0:8: Not in scope: data constructor `Color'
*Main typeOf PersonType
interactive:0:8: Not in scope: data constructor `PersonType'
But, I'd like to start processing of data definition from the *type
constructor*. So:
emit_proto PersonType 1
emit_proto Color 1
Is that possible at all? I mean in the scope/context of GHC's
Data/Data.Data/Data.Typeable etc. modules. (w/o considering TH now).
A definition of 'typeOf' is not supposed to use its argument, since
the normal way to call it is to pass undefined. The documentation
says:
The value of the argument should be ignored by any instance of
Typeable, so that it is safe to pass undefined as the argument.
So you should call it like:
typeOf (undefined :: PersonType).
Erik
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Re: [Haskell-cafe] DSL for data definition (e.g. compiling Haskell type defs into Google's protocol buffers type defs)
On 10/4/11 12:02 PM, Karel Gardas wrote: Hello, I'm trying to find out if it's possible to use Haskell data type definition capability to define types and compile defined types into other languages, for example into Google's protocol buffers data definition language. So basically speaking I'm thinking about using Haskell sub-set as a data-definition DSL together with some functions which will generate some code based on supplied defined data types. My idea is: If your main goal is to use protocol buffers in Haskell, then I'd recommend checking out Chris Kuklewicz's packages: hprotoc, protocol-buffers, protocol-buffers-descriptor. If your main goal is actually to have a DSL, well, the other folk's comments about generic programing techniques should help. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
