Methods in VHDL

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity Rectangle is
    Port ( width : in INTEGER;
           height : in INTEGER;
           area : out INTEGER;
           perim : out INTEGER );
end Rectangle;

architecture Behavioral of Rectangle is
begin
    -- This process calculates the area
    area_proc: process(width, height)
    begin
        area <= width * height;
    end process;

    -- This process calculates the perimeter
    perim_proc: process(width, height)
    begin
        perim <= 2 * width + 2 * height;
    end process;
end Behavioral;

-- Testbench
entity Rectangle_TB is
end Rectangle_TB;

architecture Behavioral of Rectangle_TB is
    component Rectangle is
        Port ( width : in INTEGER;
               height : in INTEGER;
               area : out INTEGER;
               perim : out INTEGER );
    end component;

    signal width, height, area, perim : INTEGER;
begin
    UUT: Rectangle port map (width => width, height => height, area => area, perim => perim);

    stim_proc: process
    begin
        width <= 10;
        height <= 5;
        wait for 10 ns;
        
        report "area: " & INTEGER'image(area);
        report "perim: " & INTEGER'image(perim);
        
        wait;
    end process;
end Behavioral;

VHDL supports entity-architecture pairs, which are similar to structs with methods in other languages. In this example, we define a Rectangle entity with width and height as inputs, and area and perim as outputs.

The area_proc process calculates the area of the rectangle, similar to the area method in the original code. The perim_proc process calculates the perimeter, similar to the perim method.

In VHDL, we don’t have the concept of pointer or value receivers as in some other languages. Instead, we use signals to communicate between processes and entities.

The testbench (Rectangle_TB) instantiates the Rectangle entity and provides test stimuli. It sets the width to 10 and height to 5, then reports the calculated area and perimeter.

To simulate this VHDL code, you would typically use a VHDL simulator. The simulation would produce output similar to:

# area: 50
# perim: 30

Note that VHDL is primarily used for hardware description and simulation, so the concept of “running” the code is different from software languages. Instead, you would simulate the design in a VHDL simulator.

VHDL doesn’t have the same concept of automatic handling of values and pointers as in some other languages. In VHDL, all communication between processes and entities is done through signals, which are somewhat similar to pointers in that they provide a level of indirection.