[kepler-dev] Re: type signatures in the expression language

Tobin Fricke tobin at splorg.org
Sat Aug 14 18:26:57 PDT 2004

On Tue, 3 Aug 2004, Stephen Andrew Neuendorffer wrote:

[about making names of internal functions like 'map' or 'sin' evaluate to

> Unfortunately, implementing this in practice is a little hard, since the
> map() function is discovered through Java's reflection mechanism which
> searches for methods with particular arguments... The 'right' thing to
> do is to find all of the functions with the name 'map' with the correct
> number of arguments, and return a function closure that invokes the
> right Java function based on the type of the arguments.

> If we wanted to get really fancy, then we could process all of the
> methods at startup and build big lookup tables for every set of function
> arguments and every function name, what is the right java method to
> invoke.  Note that Java and C++ do not do this, since the tables can
> grow large when you are performing method selection based on all the
> arguments.

Are there any obstacles to doing it the first way, avoiding compiling huge
tables?  When a name is not found in the symbol table, the system could
use reflection to see if the name resolves to anything that way.  I.e. if
'map' isn't found in the symbol table, then the reflection mechanism would
search (in UtilityFunctions, I guess) for functions named 'map' with any
return type and any argument type.  I suppose one problem is what to do in
the case of overloading -- if there are multiple functions with the same
name but different argument types.  Are there any overloaded functions
accessible from the expression language already?

The functions to extract a subarray are a tempting area for overloading.
It seems sort of silly to create distinctly named functions for the (int),
(int, int), ({boolean}), and ({int}) argument types, since the function
names would be more-or-less synonimous ("get", "extract", ... ?).
Another scheme would be to have distinct names for these methods within
ArrayToken and just overload the arrayname(-) syntax in the expression


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