OpenEuphoria

Re: Homogeneous sequence

• Posted by Bernie Ryan <xotron at bluef?og?com> Aug 12, 2007
• 671 views

Robert Craig wrote:
> 
> CChris wrote:
> > You are painfully aware that type checking has a O(N) complexity, where N is
> > not the legth, but the number of all atoms in all your subsequences. Reguar
> > type checking is probably very inefficient here.
> 
> This reminds me of a proposed extension to the type system
> that various people, including myself, have thought about before.
> It would be intuitively clear, and somewhat useful, to allow
> type declarations such as:
> }}}
<eucode>
>   sequence of integer x
>   sequence of object x
>   sequence of sequence x
>   sequence of sequence of atom x
>   sequence of my_user_defined_type x
>   etc.
> </eucode>
{{{

> 
> In many cases this would reduce the type-checking cost from
> O(n) to O(1), since the type-check could be limited to a
> single value, e.g.
> 
>   x[5] = expression
> 
> would only have to test x[5], not all of x, as you would need
> today if you made your own user-defined type that loops over
> all of x to enforce that it only contain elements of say
> integer, or some other type.
> 
> Stricter types would help to catch bugs earlier in the code, 
> and document variables more precisely.
> 
> Type information, such as this, could also in many cases 
> help the Translator to produce slightly faster C code.
> 
> I spent a lot of time thinking about this a few years ago.
> I didn't proceed with it because:
>   
>   * I was worried that since the existing user-defined type
>     system is not used all that much, perhaps this enhancement
>     to the type system would not be used much either. People 
>     might be content to just say:
>          sequence x
>     rather than the much wordier:
>          sequence of integer x
>     On the other hand, this enhancement might encourage much more
>     use of user-defined types.
> 
>   * Newbies might be confused, and put off by all this, 
>     thinking it was somehow necessary to provide full and proper
>     types for everything.
> 
>   * It seemed at the time to be a fair bit of work, and extra 
>     baggage added to the language, for just a small gain.
> 
>   * In many cases, the Translator deduces this information by
>     examining all uses of a variable across the whole program.
> 
> But perhaps we should reconsider this idea.
> 
> Regards,
>    Rob Craig
>    Rapid Deployment Software
>    <a href="http://www.RapidEuphoria.com">http://www.RapidEuphoria.com</a>

This would save typing:

  seq_of_int x
  seq_of_obj x
  seq_of_seq x
  seq_of_seq_of atom x
  seq_of_udt x

Bernie

My files in archive:
WMOTOR, XMOTOR, W32ENGIN, MIXEDLIB, EU_ENGIN, WIN32ERU, WIN32API 

Can be downloaded here:
http://www.rapideuphoria.com/cgi-bin/asearch.exu?dos=on&win=on&lnx=on&gen=on&keywords=bernie+ryan