too many declarations of - oracle

Question

I am getting the following error message while running the below code. I am new to coding world of pl/sql (oracle) and I request your assistance for the same.
Code:
create or replace package learn is
function Area(i_rad NUMBER) return NUMBER;
function Area(i_length NUMBER, i_width NUMBER:=3) return NUMBER;
end;
/
Package body:
create or replace package body learn is
function Area(i_rad NUMBER) return NUMBER
is
v_pi NUMBER:=3.14;
v number:=to_number(i_rad);
begin
return v_pi * (i_rad ** 2);
end;
function Area(i_length NUMBER, i_width NUMBER:=3) return NUMBER
is
begin
return i_length * i_width;
end;
end learn;
Plsql block
declare
x number(2):=2;
y number(2):=5;
begin
DBMS_OUTPUT.put_line('Area (R=3):'||learn.Area(x));
DBMS_OUTPUT.put_line('Area (R=3):'||learn.Area(x,y));
end;
Error Message: too many declarations of 'AREA' match this call

Answer 1

That's because you have default value for the second parameter in your two param function. If you provide only param, the second function will assume the second value to be 3 and now there are two functions that can be called and hence the call failed.
I'd suggest you not to do this kind of overloading as it is not clear which function does what.
If you still want to do this, one way is to make the second param mandatory and pass null if you don't have any value to pass.
create or replace package learn is
function Area(i_rad NUMBER) return NUMBER;
function Area(i_length NUMBER, i_width NUMBER) return NUMBER;
end;
/
create or replace package body learn is
function Area(i_rad NUMBER) return NUMBER
is
v_pi NUMBER:=3.14;
v number:=to_number(i_rad);
begin
return v_pi * (i_rad ** 2);
end;
function Area(i_length NUMBER, i_width NUMBER) return NUMBER
is
begin
return i_length * nvl(i_width,3);
end;
end learn;
/
declare
x number(2):=2;
y number(2):=5;
begin
DBMS_OUTPUT.put_line('Area (R=3):'||learn.Area(x));
DBMS_OUTPUT.put_line('Area (R=3):'||learn.Area(x,y));
end;
/
If you have different param names, you can do this:
declare
x number(2):=2;
y number(2):=5;
begin
DBMS_OUTPUT.put_line('Area (R=3):'||learn.Area(i_rad => x));
DBMS_OUTPUT.put_line('Area (R=3):'||learn.Area(x,y));
end;
/

Answer 2

Since i_width has a default value, you have two functions that can be called with a single number argument. Since both these functions calculate different areas, a good way to differentiate would be to simply use different names:
CREATE OR REPLACE PACKAGE learn IS
FUNCTION circle_area(i_rad NUMBER) RETURN NUMBER;
FUNCTION rectangle_area(i_length NUMBER, i_width NUMBER:=3) RETURN NUMBER;
-- And the same changes in the package body, of course.
END;
/