question about parentheses and square brackets

[buddhasarah]

I have a question about the usage of parentheses and square brackets in OpenSees's code. The following code is a small section from the OpenSees source code, I guess the both "connectedExternalNodes(0)" and "theNodes[0]" means the first cell of "connectedExternalNodes" and "theNodes" array respectively. But why the former uses parentheses while the latter uses square brackets? The lower code is another similar example with the same question. Thank you very much in advance!
#####################################
// Set connected external node IDs
connectedExternalNodes(0) = nd1;
connectedExternalNodes(1) = nd2;

theNodes[0] = 0;
theNodes[1] = 0;
#####################################
q(0) += q0[0];
q(1) += q0[1];
q(2) += q0[2];
#######################################

[leon1977]

Thankyou so much, it really helped alot!!

[fmk]

theNodes, q0 are array's and the [] are used in c or c++ to reference a member of the array.

q, connectedNodes are of type vector and id, these are c++ classes i have defined which have overloaded operators (). these () operators also access the components, but check the range of the indices is valid.

[billjhonson]

Thanks for the greatest news about parentheses and square brackets. It's really help to everyone.............

[linguan118]

Yes, very helpful!
Matrix belongs to arrays, right?