Re: Compile time executed functions

["Ken Garlington" <Ken.Garlington@computer.org>]

"Jean-Marc Bourguet" <jbourguet@free.fr> wrote in message
news:3AC4B7F9.7C73455A@free.fr...
: Ken Garlington wrote:
: >
: > "Jean-Marc Bourguet" <jbourguet@free.fr> wrote in message
: > news:3AC46252.B7E54EA6@free.fr...
: > : Ken Garlington wrote:
: > :
: > : > Could you post an example of such a template, and what in the C++
: > standard
: > : > you rely upon to guarantee compile-time calculations?
: > :
: > : First feature, things like
: > :    enum { foo = x+y*z; }
: > : are valid as long as x, y and z value are known at compile time and
have
: > : to be evaluated at compile time.
: >
: > Isn't this usually resolvable as a constant by most Ada compilers? At
least
: > the ones I know will usually do so.
:
: It is quite difficult to come with the equivalent in Ada.  One is
:    foo : constant = x+y*z;
: is indeed resolvable by most Ada compiler.
:
: > More to the point, does the C++ standard _require_ that foo not generate
any
: > assembly instructions to be executed at run-time? If so, what does it
say?
:
: I've not checked what the standard says precisely.  The enum values are
: a compile time constant.  They may be used in context like case label
: which are to be fixed at compile time.  This
:
: enum { a = 2, b = 3, c = 4, d = 7 };
: enum { foo = a+b*c };
: enum { bar = a*d };
:
: void f() {
:   int foobar;
:   switch(foobar) {
:     case foo:
:       break;
:     case bar:
:       break;
:   }
: }
:
: is required to produce a diagnostic as foo and bar have the same value.

Same with Ada, as far as I know.

These examples are all in terms of "the value has to be calculated as a
scalar before it is used." This is *not* the same as saying "no code is
generated at run-time".