www.digitalmars.com         C & C++   DMDScript  

digitalmars.D - Re: equivariant functions

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; }

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.
Oct 14 2008