slices ; Stroustrup & libstdc++

[llewelly@dbritsch.dsl.xmission.com]

On Sat, 17 Jun 2000, brent verner wrote:

> on Fri, Jun 16, 2000 at 12:59:00PM +0200, Gerhard Wesp typed aloud:
> |   hi all,
> | 
> |   i just tried a slice_array example from stroustrup, 3rd ed., p. 671
> | which fails with the following error:
> | 
> | grisu ~/c++% cat slice.cc 
> | #include <valarray>
> | 
> | void f(std::valarray<double>& d)
> | {
> |   std::slice_array<double>& v_even = d[std::slice(0,d.size()/2,2)];
> | }
> 
> I'm seeing the same error. I've spent the evening digging around
> valarray & friends. I can't even decide if the code above _should_
> work or not -- have you found out anything more? Would someone 
> enlighten us? I've compared the code to the standard, and everything
> _looks_ OK (by the std).
> 
> FWIW, the following code _does_ work.
> 
> #include <valarray>
> #include <iostream>
> 
> void 
> f(std::valarray<double>& d)
> {
>   std::slice oh(0,d.size()/2,2);
>   d[oh] = 100;
>   // d[oh] += d; // uncomment this to see its effect... i'm not
>                  // sure it is correct. :\ .
> }
> 
> int
> main()
> {
>   std::valarray<double> a(10);
>   f(a);
>   for(unsigned i = 0; i < a.size(); ++i)
>     std::cout << "a[" << i << "] = " << a[i] << std::endl;
>   return 0;
> }
> 
> | grisu ~/c++% g++ -fhonor-std -c slice.cc
> | slice.cc: In function `void f(std::valarray<double> &)':
> | slice.cc:5: initialization of non-const reference type `class std::slice_array<double> &'
> | slice.cc:5: from rvalue of type `std::slice_array<double>'
> | grisu ~/c++% g++ -v
> | Reading specs from /usr/local/lib/gcc-lib/i586-pc-linux-gnu/2.95.2/specs
> | gcc version 2.95.2 19991024 (release)
> | 
> |   is stroustrup wrong, or is libstdc++ (i'm using version

It might be worthwhile to check the errata for 3rd edition, at
  www.research.att.com/~bs/3rd_errata.html ; there are several errors
  mentioned on pgs 670-671.

unfortunately, I cannot find my copy of 3rd edition, and the errata are
  hard to read without one; I cannot tell what might be relevant.

> | libstdc++.so.3.0.0) wrong, or am i missing something?
> | 
> | greetings,
> | -gerhard
> 
>