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add the visitor-predicate as a second option

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contrary to the Visitor, accepting a Predicate is const,
and -- of course -- the Predicate invocation returns bool.

This can be used to implement comparison operators or
search functions on Variant based data structures.
This commit is contained in:
Fischlurch 2015-08-29 18:56:19 +02:00
parent de3726c856
commit 4c59e16f06
1 changed files with 18 additions and 2 deletions
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20
src/lib/variant.hpp
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@ -224,8 +224,9 @@ namespace lib {
virtual ~Buffer() {} ///< this is an ABC with VTable
virtual void dispatch (Visitor&) =0;
virtual operator string() const =0;
virtual void dispatch (Visitor&) =0;
virtual bool dispatch (Predicate&) const =0;
virtual operator string() const =0;
};
@ -317,6 +318,15 @@ namespace lib {
typeDispatcher.handle (this->access());
}
bool
dispatch (Predicate& visitor) const
{
using Dispatcher = VFunc<bool>::template ValueAcceptInterface<const TY>;
Dispatcher& typeDispatcher = visitor;
return typeDispatcher.handle (this->access());
}
/** diagnostic helper */
operator string() const;
};
@ -452,6 +462,12 @@ namespace lib {
{
buffer().dispatch (visitor);
}
bool
accept (Predicate& visitor) const
{
return buffer().dispatch (visitor);
}
};