Re: Principle of Uniform Reference

[dewar@cs.nyu.edu (Robert Dewar)]

Adam, in your discussion of uniform reference you say that you should not
use constants, but instead functions, but here is a case where Ada does
in fact provide uniform reference:

   x         reference to constant x
   x         call of function x

so if you decide to later replace a constant by a function, clients do
not need to be modified. of course I am assuming here that the constant
is deferred so that details of its structure are appropriately hidden.

The notion of using functions and procedures to abstract simple access
functions is certainly a reasonable one. In GNAT, all attributes in the
tree are function calls, and actually, since there are several levels
of abstraction in the data structures, a simple access to the tree, say
for the type of a node, requires three levels of function calls.

Eventually, when we implement inlining, these three levels will disappear
(but they are there today, which is why I have noted in the past that you
can expect the eventual performance of the GNAT front end to be a factor
of several faster than it is today).