This is a reference to an array of 3 doubles, right? According to 34.3.9 Pointers, references, values, and arrays, you should be able to use as is.
Otherwise, you could try 34.9.4 Mapping Python tuples into small arrays, or the section after that. Or provide further details in your question about what Python code you would like to be able to write vs the code you have to write if you just let SWIG export the bar()
function as is, without typemaps.
Update: You should also be able to %extend or %inline an adapter function that forwards to the array version, something like:
%inline %{
void bar(double* array, int length) {
typedef double triplet[3]; // array of 3 doubles
bar((triplet&)array); // shouldselect your bar since only one arg
}
%}
Warning: not tested ;)