Re: [Texmacs-dev] Efficiency of C++ switch-statements

[Joris van der Hoeven]

> |  Much more code
> | is executed in the map object.  You have to remember that a switch
> | just does assembly compare instructions.  No method calls are made
> | (which are expensive), also the cmp instruction is fairly atomic and
> | is not a CISC feature (on RISC also), so no microcode is used as is
> | the mul and div instructions which are not atomic.

This is true, I also prefer not to use a software hashtable
(also because I would have to fill out the entries anyway,
so why not use a real table in that case?).

However, it might be interesting for the compiler to create
a hashtable. The idea is that all cases are known beforehand,
so the compiler might *choose* an efficient hash function for
the particular purpose.

> But, a virtual function call may be cheaper than the series of
> compares and jumps.  And in case the compiler would have used a branch
> table, again the virtual function call may be cheaper.
[...]
> compared to a virtual function call, a switch is simpler onnly in a
> very limited cases.

I still do not see how you want to use virtual functions here.