Re: get_local() and "(for index/limit/stop)"

[Rici Lake <lua@...>]

On 18-Sep-04, at 6:08 AM, Adrián Pérez wrote:

> Moreover, if you recognize "_" as such, you can make optimizations to 
> bytecodes, for example if you do:
>
>     _, a = my_function()
>
> The compiler may skip generating bytecodes for the first argument, 
> thus gaining a bit in speed. Not a big gain, but it worths if you use 
> "_" a lot (using "_" is quite usual in functional programming).

That is probably more useful in functional languages with lazy 
evaluation; my_function() might not need to calculate its first return 
value. But in Lua, it is going to calculate it anyway; the only cycles 
saved would be a load/store.

In any event, the compiler should not need clues like this. It is easy 
enough to tell if the value of a local variable is not going to be 
used, regardless of its name. That is usually a programming error, of 
course: my Lua linter has a specific hook in it to avoid flagging 
unused local _'s in order to allow this idiom.

Rici.