-- test_passing_function.adb  simple trapezoidal integration
with Ada.Text_IO; use Ada.Text_IO;

procedure Test_Passing_function is
  Xmin : Long_Float := 1.0;
  Xmax : Long_Float := 2.0;
  N : Integer := 10;
  Area : Long_Float;
  package Lf is new Ada.Text_IO.Float_IO(Long_Float);
  use Lf;
  type Funct is access function (X : Long_Float) return Long_Float;

  function F(X : Long_Float) return Long_Float is
  begin
    return X*X;
  end F;

  function Trap_Int(F : funct; Xmin : Long_Float; Xmax : Long_Float;
                    N : Integer) return Long_Float is
    Area : Long_Float := (F(Xmin)+F(Xmax))/2.0;
    H : Long_Float := (Xmax-Xmin)/Long_Float(N);
  begin
    for I in 1..N-1 loop
      Area := Area + F(Xmin + H*Long_Float(I));
    end loop;
    return H*Area;
  end Trap_Int;
begin
  Put_Line("test_passing_function.adb running, n="&
           Integer'Image(N));
  Put("xmin="); Put(xmin,2,5,0);
  Put(", xmax="); Put(xmax,2,5,0);
  New_Line;

  area := Trap_Int(F'Access, Xmin, Xmax, N);
  Put("area="); Put(area,3,6,0);
  New_Line;

  put_line("test_passing_function.adb finished");
end Test_Passing_Function;