Re: #line specifier in Lua

[Xavier Wang <weasley.wx@...>]

2014-07-14 22:54 GMT+08:00 Roberto Ierusalimschy <roberto@inf.puc-rio.br>:
>> I just hopes to know how Luiz & Roberto think about add a #line (or
>> other syntax) to Lua, specific the line number of next line, this is
>> useful when you write a preprocessor (somethings like [1] or [2] or
>> LuaMacro[3])
>>
>> the implement may very easy: when llex read a #line, it set the
>> lastline (or linenumber?) field of LexState.
>
> It is not that easy. A #line directive without a file name is a half
> baked solution, and to store multiple file names in a chunk would
> require some new data structures. (Nothing impossible, but it is
> not trivial.)
>
> -- Roberto
>

But in Lua-spec, pre-processor needn't include file. metalua,
LuaMacro, luapp all do not support include other file. because in C,
macros and declares are in the same level with C code, and macros
operate on string, but in Lua, we don't need declare, and macros is in
the different level (compiler-time run) of Lua code, that means, we
needn't include other file to baked source.

if needed, we only require a normal lua file in the compile-time, and
using macros, some codes like this:

#local foo = require "foo"
print($(foo.bar()))

in C, #include is just simply insert text into current source file,
but in Lua, # is eval codes when convert file into baked source, all
macros lives in different level with code, and not only string but
full-functional lua objects.

I think with this concept, only liner change statement/sign is enough.


-- 
regards,
Xavier Wang.