Re: when should a variable to quoted?

[pjb@informatimago.com (Pascal J. Bourguignon)]

sunway <sunwayforever@gmail.com> writes:

> "elisp lacks of lexical variable", if this happens to the C
> programming language:
> int a=10;
> foo(a);
> may be "a" will be changed to 9 ?
>
> if so, I really hate this feature....

1- not in C, but in C++ you can have:
   void foo(int& v){ v=0; }
   void f(){
      int a=10;
      foo(a);
      assert(a==0);
   }

2- even in C, soon enough you have types such as it is possible. eg.
   typedef struct node { int item, struct node* next; } *Node_type;
   void f(void){
       Node_type a=make_node(10);
       foo(a);
       assert(a->item==0);
   }


elisp lack of lexical variables implies only that for all variable,
the symbol naming that variable holds its value and can be used as a
"pointer".  With lexical variables, once compiled there remains no
link between the symbol naming a variable and the variable.  On the
other hand, in these lisp we have real closures, so we can build a
"pointer" also named "locative" with closures.
   
-- 
__Pascal Bourguignon__                     http://www.informatimago.com/

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