This adds initial support for detecting integer variables in formulas.
The scope is somewhat limited in that variables matching predicate
parameters with known integer type aren’t propagated to be integer as
well yet. Also, the use of constants and functions prevents variables
from being detected as integer, because they have to be assumed to be
externally defined in such a way that they evaluate to general values
and not necessarily integers.
The Tristate class (representing truth values that are either true,
false, or unknown) is used at multiple ends. This moves it to a separate
header for reusing it properly.
This refactoring separates predicates from their declarations. The
purpose of this is to avoid duplicating properties specific to the
predicate declaration and not its occurrences in the program.
With this change, the domain of variable declarations can be specified.
While the default is the general domain of all precomputed value, this
adds support for integer variables, for which advanced simplification
rules apply.
cxxopts 2.1.0 has a bug preventing it from being used with standard main
signatures. This updates cxxopts to the commit after release 2.1.0,
where this issue was addressed.
The unary modulus operation does not require extra parentheses to be
printed in cases like “|X + Y|”. This adds a new option to the printing
routine to omit parentheses in cases where the parent expression already
defines a parenthesis-like scope (currently only with unary operations).
This implements a tableau containing simplification rules that can be
iteratively applied to input formulas until they remain unchanged.
First, this moves the rule “exists X (X = Y) === #true” to the tableau
as a reference implementation.
Because of a bug in the Clingo API, the exponentation operator was not
properly exposed to anthem. This updates Clingo to a version with a
fixed API and adds proper support for exponentation within anthem along
with a matching unit test.
For some reason, Bison is not implicitly installed along with the other
dependencies in the Ubuntu 18.04 image used for continuous integration.
This adds Bison explicitly.
This adds support for declaring predicates as placeholders through the
“#external” directive in the input language of clingo.
Placeholders are not subject to completion. This prevents predicates
that represent instance-specific facts from being assumed as universally
false by default negation when translating an encoding.
This stretches clingo’s usual syntax a bit to make the implementation
lightweight. In order to declare a predicate with a specific arity as a
placeholder, the following statement needs to be added to the program:
#external <predicate name>(<arity>).
Multiple unit tests cover cases where placeholders are used or not as
well as a more complex graph coloring example.
With cxxopts 2.0.0, positional arguments weren’t recognized when other
command-line options were passed before. This has been fixed in the
meantime, but there is no release with the bug fix yet.
This updates cxxopts to a newer commit to ship anthem with this fix.
Boost was only used for program option parsing. To avoid this huge
dependency, this commit replaces boost::program_options with cxxopts,
a header-only library with the same functionality.
cxxopts is added as a submodule, and Boost is removed from the
dependencies in the code and Travis configuration.
With C++17, optionals, an experimental language feature, were moved to
the “std” namespace. This makes C++17 mandatory and drops the now
obsolete “experimental” namespace.
As Travis only provides outdated packages (compilers in particular),
this changes the Travis configuration to use Docker images to build and
test the code. This also has the benefit that multiple distributions can
be tested and not just Ubuntu.
For the time being, Arch Linux and Ubuntu 18.04 are added as supported
platforms.
