
Natural for UNIX	Version 8.3.7 for UNIX	SEARCH CONTENTS \| PDF BOOKS \| HOME UP PREV NEXT

— Statements —

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:

Function
Syntax Description
Example

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

Related Statements: REPEAT | ESCAPE

Belongs to Function Group: Loop Execution

Function

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).

Syntax Description

Operand Definition Table:

Operand	Possible Structure							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: `operand4` must not be zero. The keyword `STEP` can be omitted.
`(arithmetic-expression)`	Arithmetic Expression: In place of `operand2`, `operand3` or `operand4`, any arithmetic expression may be specified. Notes: The arithmetic expressions must be enclosed in parentheses. 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`

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.

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