st: basic quesion about using structures in mata

[Matthew Weinberg <mweinber@gmail.com>]

I'm trying to use structures for the first time and am having a little 
trouble.  I want the function markups to take three arguments (s,p,b) 
and return three arguments (margins, marks, and costs).  I'm getting 
back one

My code is:

mata
struct mups{                      /*define the structure*/
real matrix margins
real matrix marks
real matrix costs
}

struct mups function markups(s,p,b)  /*define the function*/
{
struct mups scalar ms  /*declare structure variable*/
n=rows(s)
S=J(n,n,0)
for(i=1;i<=n;i++){
for(j=1;j<=n;j++){
S[i,j]=-b*s[i]*s[j]
}
}
for(i=1;i<=n;i++){
S[i,i]=-b*s[i]*s[i]+b*s[i]
}
Omega=I(n)*S
ms.margins=invsym(Omega)*s
ms.costs=p-ms.margins
ms.marks=(p-ms.costs):/p
return(ms)
}
end

When I evaluate my function, I get back what something like 0x27c65c 
instead of the three vectors margins, costs, and marks.  I'd really 
appreciate it if somebody could tell me what I'm doing wrong.  Thanks, Matt
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