Re: [rust-dev] Dynamic in Rust

[Abhijeet Gaiha]

You could define an enum that encapsulates all known types.

enum monster {
 Integer(int),
 Float(float),

}

Then use a container for this type.
On Aug 23, 2013 10:20 AM, Oren Ben-Kiki o...@ben-kiki.org wrote:

 Is it possible to implement something like Haskell's Dynamic value holder
 in Rust? (This would be similar to supporting C++'s dynamic_cast).
 Basically, something like this:

 pub struct Dynamic { ... }
 impl Dynamic {
 pub fn put(value: ~T) { ... }
 pub fn get() - OptionT { ... }
 }

 I guess this would require unsafe code... even so, it seems to me that
 Rust pointers don't carry sufficient meta-data for the above to work. A
 possible workaround would be something like:

 pub struct Dynamic { type_name: ~str, ... }
 impl Dynamic {
 pub fn put(type_name: str, value: ~T) { Dynamic { type_name:
 type_name, ... } }
 pub fn get('a self, type_name: str) - Option'a T {
 assert_eq!(type_name, self.type_name); ... } }
 }

 And placing the burden on the caller to always use the type name int
 when putting or getting `int` values, etc. This would still require some
 sort of unsafe code to cast the `~T` pointer into something and back, while
 ensuring that the storage for the `T` (whatever its size is) is not
 released until the `Dynamic` itself is.

 (Why do I need such a monstrosity? Well, I need it to define a
 `Configuration` container, which holds key/value pairs where whoever sets a
 value knows its type, whoever gets the value should ask for the same type,
 and the configuration can hold values of any type - not from a predefined
 list of types).

 Is such a thing possible, and if so, how?

 Thanks,

 Oren Ben-Kiki

 ___
 Rust-dev mailing list
 Rust-dev@mozilla.org
 https://mail.mozilla.org/listinfo/rust-dev


___
Rust-dev mailing list
Rust-dev@mozilla.org
https://mail.mozilla.org/listinfo/rust-dev

Re: [rust-dev] Dynamic in Rust

[Abhijeet Gaiha]

I think your second solution is what will work. You can use unsafe code and
a void pointer combined with a type descriptor string. I would probably
combine the void pointer and string in a struct.
On Aug 23, 2013 10:27 AM, Oren Ben-Kiki o...@ben-kiki.org wrote:

 That would require me to declare up front which types were usable and
 which weren't. I'm looking for a solution where I don't need to do that;
 that is, allow me to add new components to the system with new
 configuration parameter types, without having to go to a central source
 location and declare these types there.


 On Fri, Aug 23, 2013 at 7:54 AM, Abhijeet Gaiha 
 abhijeet.ga...@gmail.comwrote:

 You could define an enum that encapsulates all known types.

 enum monster {
  Integer(int),
  Float(float),
 
 }

 Then use a container for this type.
 On Aug 23, 2013 10:20 AM, Oren Ben-Kiki o...@ben-kiki.org wrote:

 Is it possible to implement something like Haskell's Dynamic value
 holder in Rust? (This would be similar to supporting C++'s dynamic_cast).
 Basically, something like this:

 pub struct Dynamic { ... }
 impl Dynamic {
 pub fn put(value: ~T) { ... }
 pub fn get() - OptionT { ... }
 }

 I guess this would require unsafe code... even so, it seems to me that
 Rust pointers don't carry sufficient meta-data for the above to work. A
 possible workaround would be something like:

 pub struct Dynamic { type_name: ~str, ... }
 impl Dynamic {
 pub fn put(type_name: str, value: ~T) { Dynamic { type_name:
 type_name, ... } }
 pub fn get('a self, type_name: str) - Option'a T {
 assert_eq!(type_name, self.type_name); ... } }
 }

 And placing the burden on the caller to always use the type name int
 when putting or getting `int` values, etc. This would still require some
 sort of unsafe code to cast the `~T` pointer into something and back, while
 ensuring that the storage for the `T` (whatever its size is) is not
 released until the `Dynamic` itself is.

 (Why do I need such a monstrosity? Well, I need it to define a
 `Configuration` container, which holds key/value pairs where whoever sets a
 value knows its type, whoever gets the value should ask for the same type,
 and the configuration can hold values of any type - not from a predefined
 list of types).

 Is such a thing possible, and if so, how?

 Thanks,

 Oren Ben-Kiki

 ___
 Rust-dev mailing list
 Rust-dev@mozilla.org
 https://mail.mozilla.org/listinfo/rust-dev



___
Rust-dev mailing list
Rust-dev@mozilla.org
https://mail.mozilla.org/listinfo/rust-dev

[rust-dev] Static initialisation of LinearMap

[Abhijeet Gaiha]

Hi Folks, 

Is there a way to statically initialise a LinearMap in code? Something like you 
can do with a vector.
Any other suggestions to save time for inserting a fixed set of values into a 
hash map?

Thanks,
Abhijeet

-- 
Abhijeet Gaiha
http://about.me/abhijeet.gaiha

___
Rust-dev mailing list
Rust-dev@mozilla.org
https://mail.mozilla.org/listinfo/rust-dev

Re: [rust-dev] Static initialisation of LinearMap

[Abhijeet Gaiha]

If I did write a macro, that would amount to the same thing as doing the 
inserts at run-time (I think).

I was looking for something like: static h:HashMapK,C = {(K,V),(K,V).}.
Is this possible at all? Any potential equivalents in the std/ext library to 
just writing a custom map of my own to do the same?


-- 
Abhijeet Gaiha
http://about.me/abhijeet.gaiha


On Tuesday, 2 July 2013 at 7:10 PM, Corey Richardson wrote:

 On Tue, Jul 2, 2013 at 9:26 AM, Abhijeet Gaiha abhijeet.ga...@gmail.com 
 (mailto:abhijeet.ga...@gmail.com) wrote:
  Hi Folks,
  
  Is there a way to statically initialise a LinearMap in code? Something like
  you can do with a vector.
  Any other suggestions to save time for inserting a fixed set of values into
  a hash map?
  
 
 
 LinearMap is now std::hashmap::HashMap (in 0.7 and in master). There
 is no way to have a *static* hashmap, I think (`static h: HashMapK,
 V = HashMap::new()`, would be immutable and useless), but you could
 write a macro that expands to a bunch of inserts into a hashmap. Not
 sure, though.
 
 


___
Rust-dev mailing list
Rust-dev@mozilla.org
https://mail.mozilla.org/listinfo/rust-dev

Re: [rust-dev] Mutability and borrowing

[Abhijeet Gaiha]

Trying to concurrently borrow a value twice is never going to work. 
You could write a function like double for such a situation.

-- 
Abhijeet Gaiha
http://about.me/abhijeet.gaiha


On Sunday, 2 June 2013 at 10:03 AM, Ziad Hatahet wrote:

 I have the following function:
 
 fn add_equal(x: mut Complex, y: Complex) {
 x.real += y.real;
 x.imag += y.imag;
 }
 
 Calling the function with the same variable being passed to both arguments 
 (i.e. add_equal(mut c, c)), results in the compile error:
 
 error: cannot borrow `c` as immutable because it is also borrowed as mutable
 
 I am guessing this is to avoid aliasing issues? What is the way around this?
 
 Thanks
 
 --
 Ziad 
 ___
 Rust-dev mailing list
 Rust-dev@mozilla.org (mailto:Rust-dev@mozilla.org)
 https://mail.mozilla.org/listinfo/rust-dev
 
 


___
Rust-dev mailing list
Rust-dev@mozilla.org
https://mail.mozilla.org/listinfo/rust-dev

[rust-dev] String Internment Library

[Abhijeet Gaiha]

There is an issue on Servo #282, which talks about having a uniform string
internment strategy across Rust, Spidermonkey and NetsurfCSS.

Is there any existing string internment library in Rust?
If not, any plans to provide one?
___
Rust-dev mailing list
Rust-dev@mozilla.org
https://mail.mozilla.org/listinfo/rust-dev

[rust-dev] TCP Library Selection

[Abhijeet Gaiha]

Hi,

Looks like there are three different libraries for TCP socket functionality:
Net_tcp
Uv_ll
Net::tcp

Could someone enlighten me as to which one is the recommended library to
use?
Thanks very much!

Regards,
Abhijeet
___
Rust-dev mailing list
Rust-dev@mozilla.org
https://mail.mozilla.org/listinfo/rust-dev