Re: Function calls [was: Lua and Neko comparison]

[John Belmonte <john@...>]

> On Thu, Sep 28, 2006 at 10:34:00PM +0200, Mike Pall wrote:
>>   local userops = {
>>     PI =     { arity = 0, op = math.pi }, -- arity 0 are constants
>>     sin =    { arity = 1, op = math.sin },
>>     cos =    { arity = 1, op = math.cos },
>>     ["|"] =  { arity = 2, op = bit.bor },
>>     ["<<"] = { arity = 2, op = bit.lshift },
>>     ["//"] = { arity = 2, op = function(a, b) return math.floor(a/b) end },
>>   } -- These should of course better be light functions.
>>
>>   loadstring([[
>>     local a, b = ...
>>
>>     print( PI * sin a + cos b )
>>     print( (a << 11) | (b << 3) | 5 )
>>     print( "Rici buys", 1.38 // 0.16, "apples." )
> 
> Intuitively, I don't like this.  I don't want to use a language where people
> are almost defining their own syntax inside the language.  That takes
> the evils that operator overloading can cause in C++ (people using operators
> for things unrelated to their original cause, like overriding + for "set
> union"), and makes it an order of magnitude worse, allowing making whole
> new operators.
> 
> That's not to say it couldn't be used well, just like operator overloading
> can be used well; it just seems to invite incredible abuse.  Practical
> languages can't make it impossible to write bad code, of course--people
> will--but this seems at such a level that in order to read anyone else's
> code, I'm going to have to learn their own personal sub-language first.
> 
> (I don't understand how a parser could support this, since the language
> is being defined by the language being compiled.)

Please understand that there are significant uses of Lua different than
your own, such as implementing domain-specific languages.

--John