[Ada] How do I create and use lambda functions (anonymous functions) in Ada?

In Ada, lambda functions (anonymous functions) are called "unconstrained access-to-function types". Here is how you can create and use lambda functions in Ada:

  1. Define the access type for the lambda function:
1type Lambda_Function is access function (Param1: Param1_Type; Param2: Param2_Type) return Return_Type;
  1. Define the lambda function itself:
1function Add_Integer (A, B: Integer) return Integer is
2begin
3  return A + B;
4end Add_Integer;
  1. Assign the lambda function to a variable of the access type:
1Lambda_Variable: Lambda_Function := Add_Integer'Access;
  1. Invoke the lambda function:
1Result: Integer := Lambda_Variable(10, 20);

Note: Make sure you have defined the appropriate types for the lambda function parameters (Param1_Type, Param2_Type) and return type (Return_Type).

Here's a complete example of using a lambda function in Ada:

 1with Ada.Text_IO;
 2
 3procedure Lambda_Function_Example is
 4   type Lambda_Function is access function (A, B: Integer) return Integer;
 5
 6   function Add_Integer (A, B: Integer) return Integer is
 7   begin
 8      return A + B;
 9   end Add_Integer;
10
11   Lambda_Variable: Lambda_Function := Add_Integer'Access;
12   Result: Integer := Lambda_Variable(10, 20);
13begin
14   Ada.Text_IO.Put_Line(Result'Image);
15end Lambda_Function_Example;

In this example, the program declares a lambda function Add_Integer and assigns it to the Lambda_Variable access type variable. Finally, it invokes the lambda function with parameters 10 and 20, and displays the result using Ada.Text_IO.Put_Line.