[Vm-dev] Using symbols in slang?

[Igor Stasenko]

hello,

just a thought, that it would be nice if we could use symbols in
translated code.
They don't have to carry any associated value(s) like classvars,
but instead could be used as unique identifiers.


struct sqSymbol { };

#define declareSymbol(name)  struct sqSymbol sqSym_##name
#define sqSym(name) &sqSym_##name

declareSymbol(foo);

each time translator sees code like:

(a == #foo ) ifTrue: [  ]

it could generate a following code:

if ( ((sqSymbol*)a) == sqSym(foo)) { .... }


Just a single example of application of it:

Currently a CogRTLOpcodes defines a lot of symbolic constants , like
... Jump JumpAbove JumpAboveOrEqual JumpBelow JumpBelowOrEqual ...

and the values of these constants carry no any additional semantic
load, and could be replaced by simple unique values
(which is symbol objects in smalltalk).

If i remember correctly , currently a symbol literals in method frame
are translated to strings. But in practice i think there are very few
of such uses,
because using string literals is less confusing and more intention revealing.

While using symbols in a way which i propose could simplify some code.

There is of course a different way how to translate symbols:
- a code generator could contain an incrementing counter for each
symbol it meets in code
and then and the end it generates a symbols.h file
which looks like:

...
#define foo 1
#define bar 2
..
and so on.


-- 
Best regards,
Igor Stasenko AKA sig.