🚀 go-pugleaf

In article 2ne@charnel.ecst.csuchico.edu, mcelroy@ecst.CSUChico.EDU (James Robert McElroy) writes:
>Borland sent me an upgrade offer for C++ V. 5.0.  Among
>the new features they say they support is "Explicit".
>No mention of what "Explicit" means is given.
>
>What is this critter?

A new language feature that lets you specify that a constructor is not
to be used for implicit type conversions. It has a meaning only for
constructors that can take a single argument. Example:

	class String {
	public:
		String();
		String(const char*);
		explicit String(int); // establish minimum size
	};
	String operator+(const String&, const String&);

	String s("Hello");
	String t = s + " World"; // OK, implicitly converts char* to String
	t = s + 2; // ERROR
	t = s + String(2); // OK, convert int to String explicitly

Without the "explicit", the expression s+2 would silently create a String
of capacity 2 and append it to s. Probably that isn't what the programmer
had in mind. With "explicit", the implicit conversion doesn't occur.

The last line is OK because the constructor is invoked explicitly.

---
Steve Clamage, stephen.clamage@eng.sun.com


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