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 | OEChem - C++ Theory Manual
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| OEChem - C++ Theory Manual
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In OEChem, we define a very limited set of functors called the
OEUnaryPredicate and OEBinaryPredicate. These two classes
are abstract base classes which define interfaces with the following
restrictions. First, they only return boolean. Second, they must define
an operator() which is a const function (i.e. - doesn't change
the state of the predicate). Third, the unary predicate is a template of 1
argument ArgType whose operator() must take a single argument of
type const & to ArgType. Similarly, the binary predicate is a template of
2 arguments (ArgType1, ArgType2) whose operator() must take two
arguments, one of const & to ArgType1 and another of const & to ArgType2.
Fourth, these predicates must define a virtual constructor function
(CreateCopy) which returns a pointer to a copy of the predicate.
This is useful for generating copies of a functor which has been passed
into a function as a reference to the OEUnaryPredicate base class.
Fifth, these predicates define Eval functions which are wrappers
around operator() and effectively make operator() a virtual
function.
While these restrictions may seem limiting at first glance, they actually produce a set of reliable behaviors which are quite useful. Unary predicates are used throughout OEChem as filters on the atoms, bonds, conformers, and molecules a programmer is interested in examining via iterator interfaces.
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