A CastConstructor in CeePlusPlus is similar to a CopyConstructor, except that the type of the argument is different than the type being defined; i.e.
class Foo { public: Foo (const Bar &); // more stuff };Like the CopyConstructor, the CastConstructor can be invoked either with "standard" constructor syntax:
Bar b; Foo f(b);or with "assignment" syntax
Bar b; Foo f = b;But wait...there's more. The CastConstructor also allows implicit casts to be performed, like this.
void snarf_the_foo (Foo &foo); ... Bar b; snarf_the_foo (b); // equivalent to snarf_the_foo (Foo(b));which can surprise you. The explicit keyword can be used to disable this automatic conversion. If Foo is defined as follows:
class Foo { public: explicit Foo (const Bar &); // more stuff };then silent conversions like that won't occur, and calling snarf_the_foo with a Bar argument will result in a compiler error. You can still use an explicit cast--i.e. snarf_the_foo (Foo(b)) if you want to do that.