next Statements

The next statement skips execution to the next iteration of an enclosing loop statement, called label in the syntax, as follows.

next [ label ] [ when condition ] ;

• label: A next statement with no label terminates the current iteration of the innermost enclosing loop. When you specify a loop label, the current iteration of that named loop is terminated.
  
  
• when is an optional clause that executes its next statement when its condition (a Boolean expression) evaluates TRUE.
  
  

The following example uses the next statement to copy bits conditionally from bit vector B to bit vector A only when the next condition evaluates to TRUE. The corresponding design is shown in the figure following the example.

entity example5_14 is

   port(

      signal B, COPY_ENABLE: in BIT_VECTOR (1 to 8);

      signal A: out BIT_VECTOR (1 to 8)

      );

end example5_14;

architecture behave of example5_14 is

begin

process (B, Copy_ENABLE)

begin

A <= “00000000";

for I in 1 to 8 loop

  next when COPY_ENABLE(I) = '0';

  A(I) <= B(I);

end loop;

end process;

end behave;

Figure 5.7 Circuit Design for next Statement

The example below shows the use of nested next statements in named loops. This example processes in the following manner.

• The first element of vector X against the first element of vector Y
  
  
• The second element of vector X against each of the first two elements of vector Y
  
  
• The third element of vector X against each of the first three elements of vector Y
  
  

The processing continues in this manner until it is completed.

signal X, Y: BIT_VECTOR(0 to 7);

A_LOOP: for I in X'range loop

. . .

  B_LOOP: for J in Y'range loop

    . . .

    next A_LOOP when I < J;

    . . .

  end loop B_LOOP;

. . .

end loop A_LOOP;