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module top(
input wire [3:0] inp,
output wire [3:0] out1, out2, out3, out4, out5,
output reg [3:0] out6
);
function automatic [3:0] flip;
input [3:0] inp;
flip = ~inp;
endfunction
function automatic [3:0] help;
input [3:0] inp;
help = flip(inp);
endfunction
// while loops are const-eval-only
function automatic [3:0] loop;
input [3:0] inp;
reg [3:0] val;
begin
val = inp;
loop = 1;
while (val != inp) begin
loop = loop * 2;
val = val + 1;
end
end
endfunction
// not const-eval-only, despite calling a const-eval-only function
function automatic [3:0] help_mul;
input [3:0] inp;
help_mul = inp * loop(2);
endfunction
// can be elaborated so long as exp is a constant
function automatic [3:0] pow_flip_a;
input [3:0] base, exp;
begin
pow_flip_a = 1;
if (exp > 0)
pow_flip_a = base * pow_flip_a(flip(base), exp - 1);
end
endfunction
function automatic [3:0] pow_flip_b;
input [3:0] base, exp;
begin
out6[exp] = base & 1;
pow_flip_b = 1;
if (exp > 0)
pow_flip_b = base * pow_flip_b(flip(base), exp - 1);
end
endfunction
assign out1 = flip(flip(inp));
assign out2 = help(flip(inp));
assign out3 = help_mul(inp);
assign out4 = pow_flip_a(flip(inp), 3);
assign out5 = pow_flip_b(2, 2);
endmodule
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