``Index'' Arrays

 

ZPL provides a set of constant parallel arrays named Index1, Index2, etc., These are constants that are defined by the compiler and conformable with any region whose rank is no greater than the index number. The value of an element of the i ``Index'' Array is the index of that element in the i dimension.

    A := Index1;            -- assign row indices to each element of A

There are certain restrictions on the use of these parallel variables.

• ``Index'' Arrays cannot be modified.
• The rank of an ``Index'' Array must be defined by its context: It must either be used in an expression with a parallel array or be passed to a function where a parallel array is expected as a parameter. Note that such arrays cannot be used in I/O statements (see Section 7.4) unless additional context specifies their rank. For example, the following is legal because the array A defines the rank of Index1:
  write(A+Index1);
  

  However, the following is not legal because there is no context to indicate the rank of Index1:
  

  write(A, Index1);