| Re: [Object IDL] routines that require user-supplied functions ... [message #12628 is a reply to message #12528] |
Tue, 11 August 1998 00:00  |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Darran Edmundson (dEdmundson@Bigfoot.com) writes:
> Here is a *demo* object-IDL code I wrote to illustrate a problem.
> This object integrates x^n over the interval (a,b) using the
> QROMB function. QROMB requires a user-defined function but I
> cannot manage to pass the 'poly' method.
>
> While this is a contrived example, one often wants to pass
> object method functions/procedures to other IDL routines. Is
> there a generic way of passing object methods to such intrinsic
> routines?
I don't believe there is a generic way of passing object
methods to intrinsic routines unless (perhaps) they are
written in such a way as to expect them. It is clear QROMB
has not been.
Nor have I found in the 15 minutes or so that I fooled around
with this a completely satisfactory "object-like" way to
solve this problem, although I did find a contrived solution
that uses a common block.
The idea is this: Put the self object in a common block
that can be declared in the POLY function. (It is a
restraint of the QROMB routine that POLY be defined with
one and only one parameter and that it be a vector of
values for which the function is solved.) This gets the
self object into the POLY function. BUT...not as a structure,
as an object reference.
This means that the equation to be solved can't look
like this, as it does in Darran's code:
x^(self.degree)
because the data of an object is hidden and is accessible
only by its methods. So I had to write a Get_Degree method
for the object that returns the degree of the function.
My solution looks like this:
function test4::init, degree, a, b
common polycommon, xx
; ^^^^^^^^^^^^^^^^^^^
self.degree = degree
self.a = a
self.b = b
xx = self
; ^^^^^^^^^
print, 'Integral = ', self->integral()
return, 1
end
function test4::integral
return, qromb('poly', self.a, self.b)
end
function test4::get_degree
return, self.degree
end
;^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
function poly, x
common polycommon, obj
;^^^^^^^^^^^^^^^^^^^^^
return, x^(obj->get_degree())
; ^^^^^^^^^^^^^^^^^^^^^
end
pro test4__define
struct = {test4, degree:0.0, a:0.0, b:0.0}
end
This object can be created and called like this:
t = obj_new('test4',3.0,0.0,1.0)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438, Toll Free Book Orders: 1-888-461-0155
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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