How to set a LaTeX3 variable to the value of a LaTeX3 expression that evaluates to a control sequene?

Question

I'd like to set the control sequence \my_cs to the value of some LaTeX3 expression that expands to a control sequence, e.g. to the value of

\use:c {some_other_control_sequence}

In other words, \some_other_control_sequence is an existing control sequence that is set to some value, and I'd like to set \my_cs to this value, but without writing out the control sequence \some_other_control_sequence explicitly. How can I do so?

For instance, suppose \some_other_control_sequence is a global LaTeX3 variable set to the integer 42, and suppose I'm writing a LaTeX3 function, and the name of this variable, namely some_other_control_sequence is expected to be passed in as the parameter #1, but I don't know the name of this variable at the time of writing the function. How can I set \my_cs to \some_other_control_sequence's value, namely 42, inside the function that I'm writing?

Answer 1

Each of the variable typs in expl3 has a series of set_eq functions for this task, for example

\tl_set_eq:NN \l_my_new_tl \l_my_old_tl
\seq_set_eq:Nc \l_my_new_seq { g_my_old_seq }
\dim_gset_eq:cc { g_my_new_dim } { l_my_old_dim }

Notice that both N- and c-type arguments may be used and that the scope should be correct for the variable being set.