FOR

FOR operand1

[:]=
EQ
FROM

operand2
(arithmetic-expression)

 
 

TO
THRU

operand3
(arithmetic-expression)

 
 
   

STEP  

operand4
(arithmetic-expression)

    statement
END-FOR   (structured mode only)
LOOP   (reporting mode only)

This document covers the following topics:

For an explanation of the symbols used in the syntax diagram, see Syntax Symbols.

Related Statements: REPEAT | ESCAPE

Belongs to Function Group: Loop Execution

FOR Usage

The FOR statement is used to initiate a processing loop and to control the number of times the loop is processed.

Consistency Check

Before the FOR loop is entered, the values of the operands are checked to ensure that they are consistent (that is, the value of operand3 can be reached or exceeded by repeatedly adding operand4 to operand2). If the values are not consistent, the FOR loop is not entered (however, no error message is output, except when the STEP value is zero).

FOR Syntax Description

Operand Definition Table:

Operand Possible Structure Possible Formats Referencing Permitted Dynamic Definition
operand1   S           N P I F               yes yes
operand2 C S     N     N P I F               yes no
arithmetic-expression   S           N P I F               no no
operand3 C S     N     N P I F               yes no
operand4 C S     N     N P I F               yes no

Syntax Element Description:

Syntax Element Description
operand1
Loop Control Variable (operand1) and Initial Setting (operand2):

operand1 is used to control the number of times the processing loop is to be executed. It may be a database field or a user-defined variable.

The value specified after the keyword FROM (operand2) is assigned to the loop control variable field before the processing loop is entered for the first time. This value is incremented (or decremented if the STEP value is negative) using the value specified after the STEP keyword (operand4) each additional time the loop is processed.

The loop control variable value may be referenced during the execution of the processing loop and will contain the current value of the loop control variable.

Note:
The keywords [:]=, EQ or FROM can be omitted.

operand2
operand3
TO Value:

The processing loop is terminated when operand1 is greater than (or less than if the initial value of the STEP value was negative) the value specified for operand3.

Note:
The keyword TO or TRU can be omitted.

STEP operand4
STEP Value:

The STEP value may be positive or negative. If a STEP value is not specified, an increment of +1 is used.

The compare operation will be adjusted to "less than" or "greater than" depending on the sign of the STEP value when the loop is entered for the first time.

Notes:

  1. operand4 must not be zero.
  2. The keyword STEP can be omitted.
(arithmetic-expression)
Arithmetic Expression:

In place of operand2, operand3 or operand4, any arithmetic expression may be specified.

Notes:

  1. The arithmetic expressions must be enclosed in parentheses.
  2. The preceding keyword cannot be omitted.

For further information on arithmetic expressions, see arithmetic-expression in the COMPUTE statement description.

END-FOR
End of FOR Statement:

In structured mode, the Natural reserved word END-FOR must be used to end the FOR statement.

In reporting mode, the Natural statement LOOP is used to end the FOR statement.

LOOP

FOR Example

** Example 'FOREX1S': FOR (structured mode)                             
************************************************************************
DEFINE DATA LOCAL                                                       
1 #INDEX (I1)                                                           
1 #ROOT  (N2.7)                                                         
END-DEFINE                                                              
*                                                                       
FOR #INDEX 1 TO 5                                                       
  COMPUTE #ROOT = SQRT (#INDEX)                                         
  WRITE NOTITLE '=' #INDEX 3X '=' #ROOT                                 
END-FOR                                                                 
*                                                                       
SKIP 1                                                                  
FOR #INDEX 1 TO 5 STEP 2                                                
  COMPUTE #ROOT = SQRT (#INDEX)                                         
  WRITE '=' #INDEX 3X '=' #ROOT                                         
END-FOR                                                                 
*                                                                       
END

Output of Program FOREX1S:

#INDEX:    1   #ROOT:   1.0000000
#INDEX:    2   #ROOT:   1.4142135
#INDEX:    3   #ROOT:   1.7320508
#INDEX:    4   #ROOT:   2.0000000
#INDEX:    5   #ROOT:   2.2360679
                                 
#INDEX:    1   #ROOT:   1.0000000
#INDEX:    3   #ROOT:   1.7320508
#INDEX:    5   #ROOT:   2.2360679

Equivalent reporting-mode example: FOREX1R.