This is a nice idea, but doesn't this give you a dependent type system? This means type inference is undecidable in theory, and extremely complicated in practice...
The only difference between:
<double> --> <double>
and
A sequential array (distributed in time over sequential samples) with type T1[N] --> T2[N]
is the "N", which is what makes it a dependent type system...
Lots of people have tried to put array sizes into type systems in conventional languages... It's no accident that none of them have it...
Edward
At 11:55 AM 5/26/2004 +0100, Willink, Ed wrote:
Hi Edward, Bertram, Liying
> You have hit upon something that has bothered me for some time, > and have expressed it better than I ever did... There are several > examples of this tension in the Ptolemy II library. E.g., the > FFT actor has type <double> --> <double>. Why isn't it > <[double]> --> <[double]>? It could just as well be, and I don't > know of any way to choose between these...
Surely <double> --> <double> is just wrong. It uses the COSSAP fudge to support Arrays in a non-Array tool via accidental sequences. Any type system that requires exaplanatory text, (use N successive samples) is not a type system.
For the proposed WDL, Waveform Description Language, (http://www.computing.surrey.ac.uk/personal/pg/E.Willink/wdl/wdl.html) I identified three distinct forms of array.
A conventional array (distributed over adjacent memory addresses) A spatial array (distributed in space over a multi-port/multiple ports) A sequential array (distributed in time over sequential samples)
(There is no limitation to 1D, provided the rasterising policy is well defined.)
An FFT specification therefore is always T1[N} --> T2[N]. Particular specialisations may choose different forms of array distribution.
Once these three forms are treated uniformly, it is also very easy to do automated conversions between them. For instance in Caltrop, each conversion would be just an 'assignment', with the distribution being an externally inferable property. In Ptolemy the multi-axis type lattice needed for fixed point must be extended with a further axis for the array-form lattice.
Regards
Ed Willink
------------------------------------------------------------------------ E.D.Willink, Email: mailto:[EMAIL PROTECTED] Thales Research and Technology (UK) Ltd, Tel: +44 118 923 8278 (direct) Worton Drive, or +44 118 986 8601 (ext 8278) Worton Grange Business Park, Fax: +44 118 923 8399 Reading, RG2 0SB ENGLAND http://www.computing.surrey.ac.uk/personal/pg/E.Willink ------------------------------------------------------------------------
------------ Edward A. Lee, Professor 518 Cory Hall, UC Berkeley, Berkeley, CA 94720 phone: 510-642-0455, fax: 510-642-2739 [EMAIL PROTECTED], http://ptolemy.eecs.berkeley.edu/~eal
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