st: Passing a subvector to a void function

[Joe Canner <jcanner1@jhmi.edu>]

A question for all you Mata programmers:

I am converting a Fortran 90 program to Mata and the Fortran program passes subarrays as arguments to subroutines like this:

	call idtang ( ndp, xd, yd, nt, iwk(jwipt), nl, iwk(jwipl),  iwk(jwiwl), iwk(jwiwp), wk )

where iwk is an array and iwk(jwipt) means "pass a subarray of iwk starting at element jwipt".  The subroutine modifies this subarray and passes it back.

I converted this to Mata as follows:

	idtang ( ndp, xd, yd, nt, iwk[|jwipt\.|], nl, iwk[|jwipl\.|], iwk[|jwiwl\.|], iwk[|jwiwp\.|], wk )

but iwk is empty upon return.

Is there a way to do this that will return the modified subvector and put it back in iwk at position jwipt?

I got it to work by creating a new vector ipt, setting it to iwk[|jwipt\.|] and passing it to the function, but I was hoping to avoid having to make so many substantive changes to the original code.

Thanks for your help!

Joe Canner
Johns Hopkins University School of Medicine

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