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Subject: Re: Time for a new release? 3.1.2?
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>> Scheme needs some way to define "interfaces"/"traits" that multiple data-types
>> can implement. Many Scheme implementations (including Kawa) have that, but a
>> general portable solution is highly desired.  Without that, there is no point
>> in piling on more and more libraries for more and more data types.

> This requires generics and this requires method dispatching.
> 
> Many Schemers like to pay the price for dynamic types, but are scared by the
> price for dynamic dispatching. I am still astonished why this is the case.

The efficiency debate can only be settled by profiling and benchmarking.

> Any ideas?

IMHO the right solution is:

- Specify generic collection procedures in RnRS.

- Those procedures MUST handle all the collection types in RnRS.

- The procedures SHOULD also handle extra collection types provided by 
the Scheme implementation (from SRFIs, etc.)

- The implementation MAY support user-defined generic procedures. When 
it does, the standard collection procedures SHOULD be defined using this 
framework so that users can extend them.

The RnRS number procedures are already generic, and work according to 
these principles (e.g. Kawa extends them to support quaternions). This 
approach is simple, flexible, and has stood the test of time.