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Template `std.variant.tryVisit`

Behaves as visit but doesn't enforce that all types are handled by the visiting functions.


						
				template tryVisit(Handlers...)
				;

If a parameter-less function is specified it is called when either variant doesn't hold a value or holds a type which isn't handled by the visiting functions.

Contained Functions

Name	Description
tryVisit

Returns

The return type of tryVisit is deduced from the visiting functions and must be the same across all overloads.

Throws

VariantException if variant doesn't hold a value or variant holds a value which isn't handled by the visiting functions, when no parameter-less fallback function is specified.

Example

Algebraic!(int, string) variant;

variant = 10;
auto which = -1;
variant.tryVisit!((int i) { which = 0; })();
writeln(which); // 0

// Error function usage
variant = "test";
variant.tryVisit!((int i) { which = 0; },
                  ()      { which = -100; })();
writeln(which); // -100

Authors

Andrei Alexandrescu

License

Boost License 1.0.