Re: C with embedded Lua or Lua-only program?
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- Subject: Re: C with embedded Lua or Lua-only program?
- From: Jerome Vuarand <jerome.vuarand@...>
- Date: Fri, 3 Sep 2010 11:43:56 +0200
2010年9月3日 Silas Silva <silasdb@gmail.com>:
> I've been done some research for a project of mine, regarding
> "embeddable" languages to make it extensible, and figured out that Lua
> would be the best solution for this particular situation.
>
> My question is: Lua is a language made to be embedded (like Tcl and
> Guile -- not sure about the last one), not like Python or Perl, which
> make it perfect to be used as a scripting language in a C program. But,
> over the time, lots of libraries were built on the top of Lua, that
> makes it a great general-purpose language. Should I make a C + Lua
> program or only Lua? Let me explain my problem:
>
> Over the years, I've done some GUI applications in several ways: using
> Tk, Qt, HTML forms, ncurses etc. But never found a uniform way to
> specify a GUI and generate the resulting code for a language/toolkit
> combination. I didn't find anything like that on the internet (please,
> tell me if I'm wrong) so I'll invent the wheel.
>
> This program will read a file (whose content will be a description of a
> GUI in a DSL (domain-specific language) that I intend to specify soon)
> and generate the code. So, basically, some would call the program in
> that way:
>
> program --generate qt-xml < file.dsl > output.ui
>
> program --generate html < file.dsl > output.html
>
> The DSL should be simple (similar to Tcl/Tk code):
>
> button foo -text "Foo" -x 10 -y 20
> label ...
>
> So, I though about using Lex & Yacc in C to parse the DSL, put
> everything in well defined data structures and generate the output. The
> generation rules would be in Lua scripts, something like (for HTML):
>
> -- Oversimplified example
> function button()
> print("<input type=submit>")
> end
>
> So, my questions are:
>
> 1. Is there any replacement for lex/flex & yacc/bison for Lua? How do
> you design DSLs in Lua? I thought about using Lex & Yacc + C it is a
> long standing wish of mine to learn parsers, BNF with Lex & Yacc...
>
> 2. I was thinking that it would be interesting to make the DSL
> Turing-complete, to make it easily programmable. Use Lua itself as
> the DSL would solve this problem, but what about if I need different
> syntax not present in Lua, like in "button foo ..."?
The Lua syntax is very flexible. The above example can be written :
button { 'foo', text = "Foo", x = 10, y = 20 }
With a custom metatable on _G (__index = function(_, k) return k end),
you could even have :
button { foo, text = Foo, x = 10, y = 20 }
And for something a little more advanced, you can use token filters,
which stays simple enough to design, reuses the Lua parser as much as
possible, and still directly gives you Lua objects.