Before we begin
Outcome v2 namespace
It is recommended that you refer to entities from this Outcome v2 via the following namespace alias:
namespace outcome = BOOST_OUTCOME_V2_NAMESPACE;
On standalone Outcome only, as patches and modifications are applied to this library,
namespaces get permuted in order to not to cause binary incompatibility. At some point
namespace outcome_v2
will be defined, and this will be the preferred namespace.
Until then BOOST_OUTCOME_V2_NAMESPACE
denotes the most recently
updated version, getting closer to outcome_v2
.
On Boost.Outcome only, as Boost provides no binary compatibility across releases,
BOOST_OUTCOME_V2_NAMESPACE
always expands into boost::outcome_v2
.
Online compilers
If you’ve never used them before, you will find Godbolt and Wandbox invaluable. These let you play with C++ inside your web browser.
Most of the source code snippets in Outcome have a link in their top right to the original source code on github. You can copy and paste this source code into Godbolt (if you wish to study the assembler generated) or Wandbox (if you wish to run the program).
Godbolt
Godbolt is invaluable for visualising online the assembler generated for a piece of C++, for all the major compilers and CPU architectures.
Standalone Outcome is built into Godbolt! In the right hand pane toolbar, click the libraries dropdown (currently third from the right, looks like a book), find Outcome and choose the version you want.
After this is selected, you can #include
any of these editions of Outcome:
<outcome-basic.hpp>
- An inclusion of
basic_outcome.hpp
+try.hpp
which includes as few system headers as possible in order to give an absolute minimum compile time impact edition of Outcome. See https://github.com/ned14/stl-header-heft. <outcome-experimental.hpp>
- An inclusion of
experimental/status_outcome.hpp
+try.hpp
which is the low compile time impact of the basic edition combined withstatus_code
from https://ned14.github.io/status-code/. If you are on an embedded system where binary bloat must be absolutely avoided, and don't mind the potentially unstablestatus_code
, this is definitely the edition for you. <outcome.hpp>
- An inclusion of
outcome.hpp
which brings in all the specialisations for thestd
STL types, plus iostreams support. If you don't know which edition to use, you should use this one, it ought to "just work".
Here is the first tutorial topic’s source code loaded into Godbolt: https://godbolt.org/z/p-NAho
Wandbox
Wandbox lets you place a third party header into a separate tab. It also comes with a recent Boost libraries. Either technique can be used to explore Outcome.
Here is the first tutorial topic’s source code loaded into Wandbox: https://wandbox.org/permlink/sJoeKHXSyCU5Avft