Re: [f-cpu] What's wrong here?

[Just an Illusion <illusion_to_net@yahoo.fr>]

Sorry,
I have made a little mistake, I have forgot the return line.

Just an Illusion wrote:

> Hello,
>
> The variable H and L can't be used to calculate the size of B, more 
> they are unnecessary.
>
> When you call the function inv_word with a vector, the A'HIGH and the 
> A'LOW aren't referred to the real size of the vecteur, but the part 
> connected.
>
> The good version is more like :
>
> function inv_word (A : in std_ulogic_vector) return std_ulogic_vector is
>    variable B : std_ulogic_vector ( A'HIGH downto 0);
> begin
>     for i in 0 to B'HIGH loop
>            B(i)=A(A'HIGH-i);
>     end loop; 

         return B;

>
> end inv_word;
>
> or
>
> function inv_word (A : in std_ulogic_vector) return std_ulogic_vector is
>    variable B : std_ulogic_vector ( A'LENGHT-1 downto 0);
> begin
>     for i in 0 to B'LENGHT-1 loop
>            B(i)=A(A'LENGHT-1-i);
>     end loop; 

         return B;

>
> end inv_word;
>
> Or any combinaison of both.
>
>
> Michael Riepe wrote:
>
>> Ok... can anybody tell me what's wrong with this function?
>>
>>     function inv_word(A : in std_ulogic_vector) return 
>> std_ulogic_vector is
>>         variable L : natural := A'low;
>>         variable H : natural := A'high;
>>         variable B : std_ulogic_vector(H downto L);
>>     begin
>>         for i in L to H loop
>>             B(i) := A(H+L-i);
>>         end loop;
>>         return B;
>>     end function;
>>
>> Hint: consider the possible index ranges of the argument.
>>
> Just an Illusion
>
Just an Illusion

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