====== LOOP ======
===== loop_statement =====
<code vhdl>
[ loop _label : ]
  [ iteration_scheme ] loop
      sequence_of_statements
  end loop [ loop _label ] ;
</code>

===== Parents =====
  * function_statement_part
  * procedure_statement_part
  * process_statement_part

===== Further definitions =====
==== label ====
  * [[.:bnf#identifier]]

==== iteration_scheme ====
''**while** [[.:bnf#condition]]''

''**for** //loop// _[[.:bnf#parameter_specification]]''

==== sequence_of_statements ====
''{ [[.:bnf#sequential_statement]] }''

===== Examples =====
This is an endless loop in which the signal //q// is assigned the value of //d// 1 ns after the condition //clock =`1`// has been fulfilled.
<code vhdl>
LOOP
   WAIT UNTIL clock = '1' ;
   q <= d AFTER 1 ns ;
END LOOP ;
</code>

----

This loop, which has a label, is run six times. In each pass the value of var is raised by 5.
<code vhdl>
lbl : FOR i IN 0 TO 5 LOOP
         var := var + 5 ;
      END LOOP ;
</code>

----

The While-loop is run as long as //value > 0// is valid. The statements within the loop are ignored if //value = 3// .
<code vhdl>
WHILE value > 0 LOOP
   NEXT WHEN value = 3 ;
   tab( value ) := value REM 2 ;
   value := value / 2 ;
END LOOP ;
</code>

----

These are two examples for chained **FOR** -loops which are needed to calculate the values of the elements of a two-dimensional array.

In the second example each of the **FOR** -loops has its own label. With the **EXIT** -statement the inner loop is left if //i = j// .
<code vhdl>
FOR i IN 10 DOWNTO 2 LOOP
   FOR j IN 0 TO i LOOP
      table( i, j ) := i + j - 7 ;
   END LOOP ;
END LOOP ;
</code>
<code vhdl>
lbl_1 : FOR i IN 10 DOWNTO 2 LOOP
   lbl_2 : FOR j IN 0 TO i LOOP
      EXIT lbl_2 WHEN i = j ;
      table ( i, j ) := i + j - 7 ;
   END LOOP lbl_2 ;
END LOOP lbl_1 ;
</code>