Error using shift and power operator

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Hi;

I am getting error using sla and ** operators.

I am including the following libraries:

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.STD_LOGIC_unsigned.ALL;

use IEEE.std_logic_arith.all;

use IEEE.numeric_std.ALL;

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Please, don't use numeric_std and std_logic_arith/unsigned at the same time! That makes for a lot of type confusion. Use numeric_std only.

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Shft_buff<= Shft_buff sla 8;

Chksum <= Chksum ** Rx_Buff_i;

The following errors I am getting

1)found '0' definitions of operator "sla", cannot

determine exact overloaded matching definition

for "sla"

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Regarding the sla operator, it is not defined for std_logic_vector. It is defined (in numeric_std) for unsigned and signed, but they're problematic and nobody uses them (and they may not synthesize). Instead, just use the usual shift left:

ShiftLeft : process (clk) is
begin
    if rising_edge(clk) then
        foo <= foo(foo'left - 1 downto 0) & '0';
    end if;
end process ShiftLeft;

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2) found '0' definitions of operator "**", cannot

determine exact overloaded matching definition

for "**"

plz help

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The exponent has to be:

a) a constant (compile-time) integer. It cannot be a variable and it certainly cannot be a std_logic_vector.

b) a power-of-two, which means it is implemented as a shift left.

So just use the shift left.