Re: Is there an easier way to deal with "inout" parameters
- From: Jay Carlson <nop@xxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Sun, 19 Aug 2012 23:04:11 -0400
As lua-l readers are all too aware, I'm interested in language meta-extensions
with Lua spirit. One of my particular hatreds is writing the same thing twice
in a row, or having to match up parallel parameter orders. The usual examples
are
"$pronoun had $jobcount jobs." % {pronoun=pronoun, jobcount=jobcount}
query("SELECT * FROM trips WHERE person=? AND destination=? LEFT INNER JOIN
ENOUGH sql_nonsense TO KEEP parameters OUT OF shouting_distance", "Steven",
"Mora")
I have a couple of mechanisms to deal with those. But they're all about getting
the values of lexical variables *in* to a little language, not how to get them
out. My proposal below of "buff,len=getvalue(nil,len)" has just the
repeat-yourself issue particularly irritating to me. So I understand the desire
behind inout, and I'm now irritated with myself for not poking around in that
side of the design space.
Jay
On Aug 19, 2012, at 9:04 PM, William Adams wrote:
> Yah, I realize that this is not a practical wish. I could probably be
> managed for FFI cases, but then the language would start to gain some weird
> semantic garbage. I guess I'll just have to man up and keep toughing it out.
> Probably a better scanner/converter could spot these, and come up with
> proper wrappers where necessary. but, realistically, it happens infrequently
> enough that all the cases will need to be hand inspected and tuned anyway.
>
> ===============================
>>
>> This is something a PUC-Rio Lua implementation of ffi would not be able to
>> do.
>>
>> Adding inout for ffi alone seems odd. For consistency, straight Lua
>> functions should have this ability too. Saaaay, what happens when you put
>> something which isn't a local lvalue in an inout slot?
>>
>> Multiple return values, as in
>>
>> buff, len = getvalue(nil, len)
>>
>> would not be as nifty, but preserves immutability of parameters, and has
>> well-defined semantics.
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