HP Business BASIC/XL Reference Manual - HP 3000 MPE/iX Computer Systems - Edition 1 (32715-90001)

4- 118
FOR Loops in READ statements
The READ statements in the previous examples have contained only
references to individual variables. A READ statement can contain a FOR
loop designed to assign values to specific array elements or substrings
of a string variable.
Syntax
(FOR num_var = num_expr1 TO num_expr2 [STEP num_expr3 ], input_list )
Parameters
num_var The numeric loop control variable that assumes the
values num_expr1 , num_expr1 + num_expr3 ,
num_expr1 +(2* num_expr3 ) on successive executions of the
loop body.
num_expr1 The initial value that num_var is assigned.
num_expr2 Value to which num_var is compared before the loop body
is executed.
num_expr3 Amount by which num_var is incremented or decremented.
The default is one.
input_list The list of items to be read. This is the same as for
the READ statement without the FOR loop.
A READ statement executes the following steps each FOR loop specified:
1. num_var = num_expr1
2. If num_expr3 is positive; go to step 3 else num_expr3 is negative
got to step 4.
3. If num_var <= num_expr2 , then assign data to the input_list
elements, and go to step 5; otherwise, stop.
4. If num_var >= num_expr2 , then assign data to the input_list
elements, and go to step 5; otherwise, stop.
5. num_var = num_var + num_expr3 .
6. Return to step 3 or 4 if num_expr3 is positive or negative ,
respectively.
Examples
A variable specified within a FOR loop in a READ statement must contain a
reference to num_expr1 as a subscript or substring if the data are not to
be repeatedly assigned to the same variable or array element. When
100 READ (FOR I=1 TO 4 STEP 1 A(I))
is executed, the index I assumes the values 1, 2, 3, and 4 and assigns
the data to the array elements A(1), A(2), A(3), and A(4). The statement
200 READ (FOR I=2 to 6 STEP 2, A$[I;1])
assigns the first character in each of the next three double-quoted
string literal data items to positions 2, 4 and 6 in A$.
FOR loops within READ statements can be nested; for example, the
following statement reads data into a 3-by-5 array.
250 READ (FOR I=1 TO 3, (FOR J=1 TO 5, A(I,J))