VHDL-2008 now provides relational operators that return bit or std_logic types. In the previous VHDL standard, the relational operators (=, <, >=…) returned boolean types. With the new types, code that needed to be written as:
if x = y then
out1 <= '1';
else
out1 <= '0';
end if;
Can now be written as:
out1 <= x ?= y;The following table lists the relational operators supported in Vivado.
| Operator | Usage | Description |
|---|---|---|
| ?= | x ?= y | x equal to y |
| ?/= | x ?/= y | x not equal to y |
| ?< | x ?< y | x less than y |
| ?<= | x ?<= y | x less than or equal to y |
| ?> | x ?> y | x greater than y |
| ?>= | x ?>= y | x greater than or equal to y |