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-- Challenge 101
--
-- TASK #2 � Origin-containing Triangle
-- Submitted by: Stuart Little
-- You are given three points in the plane, as a list of six co-ordinates:
-- A=(x1,y1), B=(x2,y2) and C=(x3,y3).
--
-- Write a script to find out if the triangle formed by the given three
-- co-ordinates contain origin (0,0).
--
-- Print 1 if found otherwise 0.
with Ada.Command_Line;
with Ada.Strings.Fixed; use Ada.Strings.Fixed;
with Ada.Text_IO; use Ada.Text_IO;
procedure ch_2 is
-- command line arguments
package CL renames Ada.Command_Line;
-- integer formatting
package Integer_IO is new Ada.Text_IO.Integer_IO(Integer);
type point is record
x, y : Float;
end record;
P : array (1 .. 3) of point;
P0 : point;
function point_in_triangle(P0, P1, P2, P3 : Point) return Integer is
function sign(P1, P2, P3 : Point) return Float is
begin
return (P1.x - P3.x) * (P2.y - P3.y)
- (P2.x - P3.x) * (P1.y - P3.y);
end sign;
d : array(1..3) of Float;
has_neg, has_pos : Boolean;
begin
d(1) := sign(P0, P1, P2);
d(2) := sign(P0, P2, P3);
d(3) := sign(P0, P3, P1);
has_neg := (d(1) < 0.0) or (d(2) < 0.0) or (d(3) < 0.0);
has_pos := (d(1) > 0.0) or (d(2) > 0.0) or (d(3) > 0.0);
if not (has_neg and has_pos) then
return 1;
else
return 0;
end if;
end point_in_triangle;
begin
-- read points
for i in 1 .. 3 loop
P(i).x := Float'Value(CL.Argument(i*2-1));
P(i).y := Float'Value(CL.Argument(i*2));
end loop;
P0.x := 0.0;
P0.y := 0.0;
Integer_IO.Put(point_in_triangle(P0, P(1), P(2), P(3)), 0);
Put_Line("");
end ch_2;
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