On Saturday, 27 September 2014 at 11:26:33 UTC, ponce wrote:
I'm dabbling with Scheme interpreter and ultimately I would
need to declare the following types.
--------------
struct Function
{
Environment env;
Atom params;
Atom body_;
}
// An atom is either a string, a double, a symbol, a function
or a list of atoms
alias Atom = Algebraic!(string, double, Symbol, Function,
This[]);
--------------
These definitions can't work since Function and Atom need each
other in this recursive definition.
How to get out of this trap?
Do I have to drop Algebraic and go back to manual tagged unions?
You can also use a pointer to a Function. Basically, any
indirection will solve this problem, whether it be via class or
pointer.
struct Function
{
Environment env;
//Either do this:
Atom* params;
Atom* body_;
}
//Or this //Now a pointer
alias Atom = Algebraic!(string, double, Symbol, Function*,
This[]);
Also, you might want to use This* instead of This[], unless you
want an Atom to be able to contain a whole array of other atoms.
