CODEWITHSUNDEEP
ada
Mawg
Mawg

Reputation: 40150

What does generic type X is (<>); mean?

just what the title asks. I am trawling through some Ada code & came across

generic type X is (<>);

What does it mean? Is it something like a C++ template parameter?

Upvotes: 1

Views: 237

Answers (1)

egilhh
egilhh

Reputation: 6430

A generic in Ada is either a package, procedure or function, with one or more formal parameters. A formal parameter can be an object, a type, a package or a subprogram. When instantiating a generic, you have to provide actuals for all the formal parameters.

generic
   type X is (<>); -- formal parameter
procedure Foo(Item : in X);

In this declaration Foo is the generic, and X is a formal parameter. The (<>) means that when you instantiate Foo, the actual for X must be of a discrete type (a signed integer type, a modular type, or an enumeration type):

procedure Bar is new Foo(Character);

Bar is now an instance of the generic procedure Foo, and can be called with a parameter of type Character:

Bar('@');

Upvotes: 6

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