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IF Performs a specified action based on a conditional test. Syntax IF condition-clause THEN statement [ELSE statement]; IF specifies tests to be performed on test-variables . IF introduces a condition-clause, which contains one or more conditions, each made up of a test-variable, a relational-operator, and one or more values. Multiple conditions are joined by AND or OR. If the condition clause is true, then the specified statement is performed. You can provide an alternate statement to be performed if the condition is not true by including the ELSE clause. If you do not include an ELSE clause and the condition is not true, control passes to the statement following the IF statement.
NOTE Do not terminate the statement preceding the ELSE clause with a semicolon (;).
Statement Parts condition- One or more conditions, connected by AND or OR, where clause AND A logical conjunction. The condition clause is true if all of the conditions are true; it is false if one of the conditions is false. OR A logical inclusive OR. The condition clause is true if any of the conditions is true; it is false if all of the conditions are false. Each condition contains a test-variable, relational-operator, and one or more values in the following format: test-variable relational-operator value [,value]... test- Can be one or more of the following: variable (item-name The value in the data register [(sub- that corresponds to item-name. script)]) The item-name can be subscripted if an array item is being referenced. (See "Array Subscripting" in Chapter 3.) [arithmetic An arithmetic expression expression] containing item names and/or constants. The expression is evaluated before the comparison is made. _________________________________ NOTE An arithmetic-expression must be enclosed in square brackets ([ ]). _________________________________ EXCLA- Current status of the automatic MATION null response to a prompt set by a user responding with an exclamation point (!) to a prompt. (See "Data Entry Control Characters" in Chapter 5.) If the null response is set, the EXCLAMATION test variable is a positive integer. If it is not set, it is zero. The default is 0. FIELD Current status of FIELD command identifier. If a user qualifies a command with FIELD, the FIELD test variable is a positive integer. Otherwise, it is a negative integer. The default is <0. INPUT The last value input in response to the INPUT prompt. PRINT Current status of PRINT or TPRINT command qualifier. The PRINT test variable is an integer greater than zero and less than 10. If a command is qualified with TPRINT, PRINT is an integer greater than 10. If neither qualifier is used, PRINT is a negative integer. The default is <0. REPEAT Current status of REPEAT command qualifier. If a user qualifies a command with REPEAT, the REPEAT test variable is a positive integer. Otherwise, REPEAT is a negative integer. The default is <0. SORT Current status of SORT command qualifier. If a user qualifies a command with SORT, the value of the SORT test variable is a positive integer. Otherwise SORT is a negative integer. The default is <0. STATUS The 32-bit integer value of the status register set by the last data set or file operation, data entry prompt, or external procedure call. relational Specifies the relation between the test-variable operator and the value. It can be one of the following: = equal to <> not equal to < less than <= less than or equal to > greater than >= greater than or equal to value The value against which the test-variable is compared. The value can be an arithmetic expression that will be evaluated before the comparison is made. The allowed value depends on the test variable, as shown in the comparison below. Alphanumeric strings must be enclosed in quotation marks. If the test- The value must be: variable is: item name Then value must be an alphanumeric string, a numeric value, an arithmetic expression, a reference to a variable as in (item-name), or a class condition as described below. [arithmetic A numeric value, an arithmetic expression] expression, or an expression, or a reference to a variable as in (item-name). INPUT An alphanumeric string. EXCLA- A positive or negative integer or MATION expression. FIELD PRINT REPEAT SORT STATUS A 32-bit integer number or expression. If more than one value is given, then: * The relational-operator can be only "=" or "<>". * When the relational operator is "=", the action is taken if the test-variable is equal to value1 OR value2 OR...valuen. In other words, a comma in a series of values is interpreted as an OR. * When the relational operator is "<>", the action is taken if the test-variable is not equal to value1 AND value2 AND... valuen. In other words, a comma in a series of values is interpreted as an AND when the operator is "<>". When the test variable is an item-name, the value can be one of the following class conditionals, which are used to determine whether a string is all numeric or alphabetic. The operator can only be "=" or "<>". NUMERIC This class condition includes the ASCII characters 0 through 9 and a single operational leading sign. Leading and trailing blanks around both the number and sign are ignored. Decimal points are not allowed in NUMERIC data. This class test is only valid when the item has the type X, U, 9, or Z, or when the item is in the input register. ALPHABETIC This class condition includes all ASCII native language alphabetic characters (upper and lowercase) and space. This class test is only valid for items of type X or U or when the item is in the input register. ALPHABETIC- This class condition includes LOWER all ASCII lowercase native language alphabetic characters and space. This class test is only valid for items of type X or U or when the item is in the input register. ALPHABETIC- This class condition includes UPPER all ASCII uppercase native language alphabetic characters and space. This class test is only valid for items of type X or U or when the item is in the input register. statement Any simple or compound Transact statement; a compound statement is one or more statements bracketed by a DO/DOEND pair. Order of Evaluation When complex conditions are included, the operator precedence is: * Arithmetic expressions are evaluated. * Truth values are established for simple relational conditions. * Truth values are established for simple class conditions. * Multiple value conditions are evaluated. * Truth values are established for complex AND conditions. * Truth values are established for complex OR conditions. Parentheses can be used to control the order of precedence when conditional clauses are being evaluated. In multiple value conditions, evaluation terminates as soon as a truth value is determined. Examples This statement causes a program branch to the "PROCEED" label if "YES" or "Y" was input in response to the INPUT prompt. If INPUT contains any other value, control passes to the next statement. IF INPUT = "YES", "Y" THEN GO TO PROCEED; This statement causes a program branch to the "TOO-HIGH" label if the data register value for the item-name COUNT is greater than 3. IF (COUNT) > 3 THEN GO TO TOO-HIGH; This statement causes an exit from the current command sequence if the status register value does not equal 0. IF STATUS <> 0 THEN END; The statements within the first DO/DOEND pair execute if the value in the input register is "Y". Otherwise, if the value for A equals the value for B, the statements at the label SAME-PART are executed. The value for D is moved to the space reserved for A if: * INPUT does not equal "Y", and * A equals B, and * A equals C, and * D is less than 50. The statements at label MORE-INFO are executed if: * INPUT does not equal "Y", and * A does not equal B. IF INPUT = "Y" THEN DO DISPLAY "PART NUMBER IS": PART-NO; PERFORM ADD-INFO; DOEND ELSE IF (A) = (B) THEN DO DISPLAY "DUPLICATE ENTRY"; PERFORM SAME-PART; IF (A) = (C) THEN IF (D) < 50 THEN MOVE (A) = (D); DOEND ELSE PERFORM MORE-INFO; The next example gives the user a choice between two activities. The second ELSE construct checks to see that the user did one of the two specified activities. If he did not, a message is displayed, and control returns to the label OPTION at the third line, so that the user is prompted again. SYSTEM IFS; DEFINE(ITEM) FIELD I(2); OPTION: PROMPT FIELD; IF (FIELD) = 1 THEN DO DISPLAY "FIELD = 1"; DOEND ELSE DO IF (FIELD) = 2 THEN DO DISPLAY "FIELD = 2"; DOEND ELSE DO DISPLAY "YOU MUST ENTER 1 OR 2"; GO TO OPTION; DOEND; DOEND; END; The next examples demonstrate how to use complex conditionals. IF (LAST-NAME) = "SMITH" AND (FIRST-NAME) = "JACK" THEN ... IF (ACCT-BALANCE) < 0 OR (LOAN-AMOUNT) >= (LOAN-MAX) THEN ... IF (RENTAL-OFFICE) = "098","978","656" AND (CUST-NO-PREFIX) = (PREFERRED-PREFIX) OR (CUST-NAME) = "ABCINC" THEN ... WHILE (BALANCE) < 0 AND STATUS = 0 DO GET(CHAIN) CUST-DETAIL,STATUS; LET (BALANCE) = (BALANCE) + (AMOUNT); DOEND; REPEAT DO LET (TOTAL-OVERDUE) = (TOTAL-OVERDUE) + (AMT-OVERDUE); FIND(SERIAL) CUST-INVOICE,STATUS; DOEND UNTIL (TOTAL-OVERDUE) > 999999.99 OR (TOTAL-OVERDUE) > (MIN-OVERDUE) AND (CUST-CODE) = "NEW"; The next examples demonstrate the use of the relational operator "<>" with multiple values. IF (STATE) <> "OR","CA","CO","VA" THEN ... WHILE (PART-NO-PREFIX) <> (PROTOTYPE),(DEVELOPMENT) GET(CHAIN) PART-DETAIL,STATUS; The next examples demonstrate the use of class conditionals. IF INPUT = ALPHABETIC THEN ... ELSE ...; DATA (PART-NUMBER); IF (PART-NUMBER) <> NUMERIC THEN ...; The next example demonstrates the use of multiple expressions in test-variables or in values. IF (AREA) = [(LENGTH)*(WIDTH)],[(BASE)*(HEIGHT)*.5], [(3.1416)*(RADIUS)**2] THEN ...; REPEAT FIND(SERIAL) STK-ON-HAND,STATUS UNTIL ((WEIGHT) > [(KILO-PER-METER) * (METERS)] AND (METERS) > (MIN-LENGTH) OR (PRICE) > [(UNIT-PRICE) * (KILO-PER-METER) * (METERS)]); IF [(DELAY) * (DFACTOR)] = [(COUNT) * 3] THEN ...;