• ore-sama <spam here.lot> Oct 14 2008

ore-sama <spam here.lot> writes:

Andrei Alexandrescu Wrote:

 I'm glad there's interest in equivariant functions. Let me share below 
 how I think they can be properly typechecked.
 
 The general signature of an equivariant function is:
 
 typeof(expression_involving(pk)) fun(T1 p1, ..., Tk pk, ..., Tn pn);
 
 Let's see this typechecking at work:
 
 1. Accessing a field:
 
 typeof(s.ptr) at(const char[] s, uint i) { return s.ptr + i; }
 
 Typecheck with a typedef for const char[], yielding:
 
 typedef const(char[]) __Surrogate;
 typeof(__Surrogate.init.ptr) at(__Surrogate s, uint i)
 { return s.ptr + i; }
 
 Pass.


How to typecheck it in the case of mutable argument?
typedef surrogate as mutable type?

In all three variants of function only const and/or equivariant methods should
be called on surrogated parameter.