HP 3000 Manuals HP 3000 Manuals
IF Command
The IF command conditionally executes some logic commands as a result of
testing one condition or a combination of two conditions.
Formats
IF condition_1 [{&}condition_2] THEN command(s) ELSE command(s)]
[{|} ]
Where & - AND, and | - OR
and condition_1 and condition_2 can be:
operand relational_operator operand
operand *BLANK
operand *ALPHA
operand *NULL
operand *NUMERIC
switch_name *ON
switch_name *OFF
Window
![[]](../../pic3k/M012319/FFN193c50.gif)
Parameters
condition_1, condition_2
The condition being tested. The condition may be testing the
relationship between two operands, the content of an operand, or the
status of a switch.
operand
The item being compared. This item may be compared with another item, or
its content may be tested for a certain status. The operand may be one
of the following:
* Whole number.
* Literal.
* Numeric or alphanumeric constant.
* Variable or calculated item.
* Screen field reference.
* Scratch-pad field reference.
* File record field reference.
* Work area field reference.
* Communication area field.
Operand Content Test.
Tests the contents of one operand. The test can be one of the following:
Test Name Meaning
*BLANK Is operand all spaces?
*ALPHA Is operand all letters? (Leading and trailing
spaces are ignored)
*NULL Does operand contain a null value? This test is
only valid if the operand is a field on a record
layout for an HP ALLBASE/SQL table or a select
list.
*NUMERIC Does operand meet N or S edit code requirements?
You cannot use these tests if the operand is a literal.
relational_operator
Tests the relationship between two operands. The relational operator may
be one of the following:
Relational Meaning
Operator
= equal to
<> not equal to
> greater than
>= greater than or equal to
< less than
<= less than or equal to
When you use a relational operator to compare two operands, the edit code
of the operands determines the nature of the relational comparison. If
you compare two numeric fields, the comparison is made on strict numeric
order. If you compare two alphanumeric fields, or compare an
alphanumeric field against a literal, the comparison is made on a
character-by-character basis using the system collating sequence (refer
to appendix A).
NOTE If you use a relational operator to compare two fields, make sure
that both fields have the same edit code, or contain similar types
of data.
switch_name
The name of the switch to be tested. The switch name can be one of the
following:
* A number in the range 1 to 8, representing one of the eight user
switches.
* *SHOWING.
* *ENTERED.
* *BYPASS.
* *ENDLINE.
* *MOREREC.
The status of the switch may be *ON or *OFF.
command
May be any logic block commands except:
* IF.
* IFLOOP.
* SELECT.
If you use more than one command, separate the commands with semicolons.
Some logic commands allow you to specify an optional command to be
executed if an error condition occurs. These are the CALC, DATE, FILE,
MATH, MATHLOOP and VALIDATE commands. If you use one of these commands
in the THEN command list or the ELSE command list of an IF command, you
must include the error condition command. If you don't, HP ALLBASE/4GL
interprets the next command in the command list as the error command, and
will only execute it if an error occurs in the previous command.
Description
The IF command tests one or two conditions and then performs one or more
commands, depending upon the result of the conditional test. For
repeatedly performing a conditional test, use the IFLOOP command.
The IF command can test the following conditions:
* The status of a switch.
* The contents of an operand.
* The relationship between two operands according to a relational
operator.
You can test more complex combinations of conditions with a decision
table. Refer to chapter 11 for more information about decision tables.
When HP ALLBASE/4GL is comparing two operands of unequal length according
to a relational operator, it extends the shorter of the two operands with
spaces until it is the same length as the other operand.
The IF command tests if the condition is true or false:
* If the condition is true, the THEN command(s) are executed.
* If the condition is false, the ELSE command(s) are executed if you
have specified any. The argument ELSE and its associated commands
are optional. If you don't specify any ELSE arguments, no
commands are executed if the condition is false.
The IF command can test a compound condition consisting of two different
conditions. In this case, a Boolean or logical AND or logical OR
operator links the two conditions. The system tests the compound
condition as one condition.
The following statements illustrate the use of the AND/OR logic:
condition_1 AND condition_2
In this situation both condition_1 and condition_2 must be true before
the compound condition is true. If either condition is false, then the
compound condition is false.
condition_1 OR condition_2
In this situation at least one of condition_1 or condition_2 must be true
before the compound condition is true. If both conditions are false,
then the compound condition is false.
HP ALLBASE/4GL uses the following symbols to specify the AND or OR
logical connectives:
Symbol Meaning
& AND
| OR
Example 1
IF *ENTERED *OFF THEN CLEAR *S; EXIT
This command tests the status of the *ENTERED switch. If *ENTERED is off
then HP ALLBASE/4GL clears all screen fields and then exits the logic
block. If *ENTERED is on, HP ALLBASE/4GL executes the next logic
command.
Example 2
IF * = "A" | * = "C" THEN ZIP ELSE VISIT delete_rec
This command checks the contents of the current screen field. If the
field contains either the letter A or C, no action is taken. If the
field contains neither of these letters, HP ALLBASE/4GL executes the
function delete_rec. In either case, HP ALLBASE/4GL then executes the
next command after the IF command.
Example 3
IF V-code &<> "NEW" THEN SERIES 10 20; ENTER 1
This command tests the content of the variable code. If the variable
doesn't contain the string NEW, HP ALLBASE/4GL executes command step
numbers 10 through 20. Processing then returns to step 1.