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Jérôme VUARAND wrote:
2007/2/25, Thomas Harning Jr. <harningt@gmail.com>:On 2/25/07, Matthew A. Nicholson <matt@matt-land.com> wrote: Great job on the library, however I think it could use a little fixing for the 'as' function. Passing in a variable of the type in order to get C++ to know what type to use doesn't sound like the best idea. Using C++ templates seems to make the most sense to me. Instead of: int val = L.as(0, index); It would be: int val = L.as<int>(index); ... Just my 2 cents.I was about to make the same suggestion. And if your original intention was to write more generic code like : int val; val = L.as(val, index); with a modern compiler you could write : int val = L.as<typeof(val)>(index); Not all compiler support the typeof operator yet, but GCC does and template based limited implementations exist for those that don't.
Hmm looking at this some more, it was a little more complicated to do than I initially estimated. I will also change the state::is() variety of functions to match. The main problem was with the default template implementation. I tried to make it so it wouldn't compile if you used it.
template<typename T>
T as(T default_value, int index = -1) {
T t;
t.unsupported_type_used_with_template();
return default_value;
}
template<typename T>
T as(int index = -1) {
T t;
t.unsupported_type_used_with_template();
throw bad_conversion("Cannot convert non value to unknown type");
}
Template specializations for each type implement the rest. I might
change the defaults to default to using lua_tonumber, as that should
also work in detecting usage errors, and cut down on the amount of code.
-- Matthew A. Nicholson matt-land.com