Názory k článku Operátory a asociativní pole v jazyku Lua

pravda, je to velmi ale velmi podobné :-) Samozřejmě je to chyba, opravíme. Má tam být:

pole={klic1="hodnota1", klic2="hodnota2", }

Opraveno, diky za upozorneni.

Pravda, taky mě to zpočátku zarazilo, autoři tu absenci vysvětlují po svém, cituji:

"
Why does Lua lack the += operator, etc.?
One of Lua's design goals is simplicity. Most languages are large, meaning that they have many sophisticated features built-in. Examples are C, C++, Python, Lisp, ML. A very few languages are small. Examples are Forth and Lua. Lua aims to provide a small range of atomic features which are truly essential, and from which many other sophisticated features can be constructed if desired. Examples of sophisticated features which can be added to Lua from within the language include modules, object orientation, and now exceptions and threads which can be implemented via coroutines in Lua 5. The absent += operator is one more example.

I thought the reason was more practical. Many argue for adding these operators because of the efficiency gains they enable. But in Lua things would get confusing because of the extension system. It's in the lua-l archives somewhere... --JohnBelmonte

I think it's more basic than that - you must draw a line in the sand for the amount of operators a small language should have. You allow +=, then people ask why not *= and -= etc etc. Before you know it, you have added many operators which simply makes it bigger. Small and simple is Lua's tenet.
"

da se s tim zit (i kdyz nekdy skripu zuby), nebo pouzit tuto techniku:

http://lua-users.org/wiki/CustomOperators

jj, s Metalua se daji delat veci... <flame>takový čitelnější Lisp :-)</flame>

Taky je zde otazka, jakou by ty operatory mely semantiku, protoze prirazeni v Lua je trosku obecnejsi, nez prirazeni v ceckovych jazycich. Urcite by se to dalo zadefinovat, ale mozna by to bylo trosku zmatecne (coz je presne proti tendencim, kam Lua miri):

a,b+=2,3

nebo jeste jinak:
a,b*=fce()

mohlo by pomoci nejake rozsireni nebo patch z: http://lua-users.org/wiki/BitwiseOperators

IMHO tam tyto operatory nejsou ze dvou duvodu:

1) je tezke definovat, co tyto operatory delaji nad defaultnim ciselnym typem, coz je v Lua double. Napriklad JavaScript (taktez s jednim typem numeric) s tim ma problemy, staci si vyzkouset v prohlizeci (adresni radek + Enter):
javascript:alert(1|2)
versus
javascript:alert(1|1.99999999999)
to druhe muze byt vysledek nejake bezne pocetni operace nad doublem, klidne i jednoduchy soucet.

2) pouziti techto operatoru je dvoji: sahani na jednotlive bity napriklad v hlavickach souboru ci protokolu - zde stejne nema smysl to delat nad doublem (viz vyse, lepsi je volat nejakou c-ckovou funkci ci pouzit patch/rozsireni) a potom bitove mnoziny (to jsou ony podminky) - zde je ovsem ve vysokourovnovem jazyku IMHO vhodnejsi pouzit skutecne bitove mnoziny, ktere nejsou omezeny na 32/64 bitu, vysledek je i citelnejsi, protoze se nemusi vytvaret nejake enum-like konstanty apod.