CODEWITHSUNDEEP
vhdl
user2514676
user2514676

Reputation: 483

VHDL assign range based on boolean constant

It doesn't seem to be possible to do something that functions like the code below in VHDL. Is this possible using some other syntax? Is there such a thing as an if statement that can be put inside the range declaration? I can't find anything online about this.

if not using_census_vector then
    variable diff : natural range 0 to ((2**cRed_pixel_bits)+(2**cGreen_pixel_bits)+(2**cBlue_pixel_bits)) * window_size * window_size - 1 := 0;
else
    variable diff : natural range 0 to ((window_size * window_size * 3 )) := 0; 
end if;

Upvotes: 1

Views: 433

Answers (1)

Tricky
Tricky

Reputation: 4471

Use a function to return the high index. Possibly no need for parameters (unless you want it common and moved to a package) because all other paramters should be in scope

function calc_high return integer is
begin
  if not using_census_vector then
    return ((2**cRed_pixel_bits)+(2**cGreen_pixel_bits)+(2**cBlue_pixel_bits)) * window_size * window_size - 1;
  else
    return ((window_size * window_size * 3 )); 
  end if;
end function

variable diff : natural range 0 to calc_high := 0;

Upvotes: 1

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