Re: use of gettop to change functionality

[HyperHacker <hyperhacker@...>]

On Tue, Mar 1, 2011 at 04:40, liam mail <liam.list@googlemail.com> wrote:
>
>
> On 1 March 2011 11:30, Gunnar Zötl <gz@tset.de> wrote:
>>
>> > The most frequent use of gettop and isnone in C lua libraries to
>> > modify what a function does really disturbs me.
>>
>> Is there a source for that claim? I'd reckon that the most frequent use of
>> these is to do optional/variable arguments, and checking wether you got the
>> correct number of arguments. At least that's what I do with those.
>>
>> > foo(nil,nil,nil) should be the same as foo(nil,nil) and foo() etc
>>
>> Nope, it should not. Passing three nils is not the same as passing nothing
>> at all.
>>
>> > What steps can we take to discourage the writing, and usage of libraries
>> > that do such evil?
>>
>> Could you name a few, please?
>>
>> Gunnar
>>
>
> Actually Daurnimator does have a valid point, which maybe should require a
> note to the functions it effects.
> I would personally say that table.insert(t,1,k) and table.insert(t,k,nil)
> under Lua rules should behave the same. The problem is the function is doing
> too much and would require a separate C function which I do not think is
> going to happen. The biggest problem I see with tinsert is that extra
> parameters ie greater than three cause an error, are there any other Lua C
> functions that do not ignore extra parameters?
>
>

Personally I would have split it into two functions:
table.insert(t, k, v, ...) --insert one or more values at position k,
shifting others as necessary.
table.append(t, v, ...) --append one or mote values.

As for gettop it has its uses, but this example is what
lua_isnoneornil() is for.

-- 
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