How to return an array in systemVerilog - verilog

Question

I am having some issues returning an array from a function in systemVerilog. However, I keep having a syntax error. I am not sure if referencing an array works here since I need to send args to my function.
Code :
module VGA_Setup
(
input wire clk, reset,
output wire hsync, vsync,
output wire [3:0] r, g, b
);
// constant declarations for VGA sync parameters
localparam H_DISPLAY = 640; // horizontal display area
localparam H_L_BORDER = 48; // horizontal left border
localparam H_R_BORDER = 16; // horizontal right border
localparam H_RETRACE = 96; // horizontal retrace
localparam H_MAX = H_DISPLAY + H_L_BORDER + H_R_BORDER + H_RETRACE - 1;
localparam START_H_RETRACE = H_DISPLAY + H_R_BORDER;
localparam END_H_RETRACE = H_DISPLAY + H_R_BORDER + H_RETRACE - 1;
localparam V_DISPLAY = 480; // vertical display area
localparam V_T_BORDER = 10; // vertical top border
localparam V_B_BORDER = 33; // vertical bottom border
localparam V_RETRACE = 2; // vertical retrace
localparam V_MAX = V_DISPLAY + V_T_BORDER + V_B_BORDER + V_RETRACE - 1;
localparam START_V_RETRACE = V_DISPLAY + V_B_BORDER;
localparam END_V_RETRACE = V_DISPLAY + V_B_BORDER + V_RETRACE - 1;
int sq_pix = 80;
wire video_on, p_tick;
int colours [3];
reg [3:0] red_reg, green_reg, blue_reg;
reg [11:0] rbg;
// mod-2 counter to generate 25 MHz pixel tick
reg pixel_reg = 0;
wire pixel_next;
wire pixel_tick;
always #(posedge clk)
pixel_reg <= pixel_next;
assign pixel_next = ~pixel_reg; // next state is complement of current
assign pixel_tick = (pixel_reg == 0); // assert tick half of the time
// registers to keep track of current pixel location
reg [9:0] h_count_reg, h_count_next, v_count_reg, v_count_next;
// register to keep track of vsync and hsync signal states
reg vsync_reg, hsync_reg;
wire vsync_next, hsync_next;
// infer registers
always #(posedge clk)
if(~reset)
begin
v_count_reg <= 0;
h_count_reg <= 0;
vsync_reg <= 0;
hsync_reg <= 0;
end
else
begin
v_count_reg <= v_count_next;
h_count_reg <= h_count_next;
vsync_reg <= vsync_next;
hsync_reg <= hsync_next;
end
// next-state logic of horizontal vertical sync counters
always #*
begin
h_count_next = pixel_tick ?
h_count_reg == H_MAX ? 0 : h_count_reg + 1
: h_count_reg;
v_count_next = pixel_tick && h_count_reg == H_MAX ?
(v_count_reg == V_MAX ? 0 : v_count_reg + 1)
: v_count_reg;
end
// hsync and vsync are active low signals
// hsync signal asserted during horizontal retrace
assign hsync_next = h_count_reg >= START_H_RETRACE
&& h_count_reg <= END_H_RETRACE;
// vsync signal asserted during vertical retrace
assign vsync_next = v_count_reg >= START_V_RETRACE
&& v_count_reg <= END_V_RETRACE;
// video only on when pixels are in both horizontal and vertical display region
assign video_on = (h_count_reg < H_DISPLAY)
&& (v_count_reg < V_DISPLAY);
// output signals
assign hsync = hsync_reg;
assign vsync = vsync_reg;
assign p_tick = pixel_tick;
colours = Letter_J(h_count_reg,v_count_reg);
// output
assign r = (video_on) ? colours[0] : 4'b0;
assign g = (video_on) ? colours[1] : 4'b0;
assign b = (video_on) ? colours[2] : 4'b0;
endmodule
function int[] Letter_J (int h_count_reg, int v_count_reg);
int colours_red = 0;
int colours_green = 0;
int colours_blue = 0;
int colours [3];
if ((h_count_reg > 160) && (h_count_reg < 400)) begin
if ((h_count_reg > 240) && (h_count_reg < 320)) begin
if ((v_count_reg > 80) && (v_count_reg < 240)) begin
colours_red = 4'b1111;
colours_green = 4'b1111;
colours_blue = 4'b1111;
end
end
end else begin
colours_red = 4'b0000;
colours_green = 4'b0000;
colours_blue = 4'b0000;
end
colours [0] = colours_red;
colours [1] = colours_green;
colours [2] = colours_blue;
return colours;
endfunction
Error :
Error (10170): Verilog HDL syntax error at VGA_Setup.sv(108) near text: "="; expecting ".", or "(". Check for and fix any syntax errors that appear immediately before or at the specified keyword...
Thank you for your help.
Joe

Answer 1

The SystemVerilog BNF requires that you use a typedef for the return type of a function when that type is an aggregate. So you must do:
typedef int intDA_t[];
function intDA_t Letter_J (int h_count_reg, int v_count_reg);