GOTO

Syntax

GOTO label

Parameters

label

The name of a label elsewhere in the program constructed following the "Guidelines for Constructing a Label". Execution of the program branches to the line directly following the specified label.

Note that label, as specified in GOTO, must not be followed by a colon. However, the actual label elsewhere in the program must end with a colon.

Usage Notes

Guidelines for Constructing a Label

When you use control structures to branch to a particular location, you must provide a label for the location to identify it clearly. When creating a label, follow these guidelines:

• The first character in the label must be a letter, period (.), or underscore (_).

• The remaining characters in a label can be any combination of letters, numbers, periods, or underscores.

• A label must be followed immediately by a colon (:).

• Ensure that the first eight bytes in the label are unique. (Remember that, in your character set, a byte might or might not be equivalent to one character.) A label can contain up to 3999 bytes (the maximum length of a text line minus 1 byte for the colon that identifies a label). However, because only the first eight bytes of a label name are used, you can experience problems with label names greater than eight bytes when the first eight bytes are not unique.

Missing GOTO Label

When an actual label that corresponds to label does not exist elsewhere in the same program, execution stops with an error.

GOTO with IF and WHILE

A GOTO statement can be used with IF...THEN...ELSE or WHILE to set up conditional branching, using the following syntax.

IF boolean-expression

   THEN GOTO label1

   ELSE GOTO label2

However, to preserve the clarity of your programming logic, minimize your use of GOTO. You can often replace GOTO with one or more statements executed conditionally using FOR, IF...THEN...ELSE, or WHILE. You can also use a SWITCH command to handle different cases within the same program.

GOTO with FOR

You can use a GOTO statement in a FOR loop to branch within, or out of, the loop which changes the sequence of statement execution, depending on where the GOTO statement and the label are positioned.

• A GOTO in a FOR loop that branches to a label within the same loop makes execution continue at the label without affecting the current dimension status. Subsequent repetitions of the loop continue normally. To branch to the end of the loop, just before the DOEND statement, consider using a CONTINUE statement instead.

• A GOTO in a FOR loop that branches to a label outside the loop terminates the effect of the FOR statement. Execution continues at the specified label and dimension status is restored to what it was before the loop. To branch to the statement immediately following the DOEND of a loop, consider using a BREAK statement instead.

When you use a GOTO statement outside a FOR loop to branch into the loop (that is, to a label inside the loop), an error occurs after execution passes through the rest of the loop once.

TEMPSTAT and GOTO Statements

Within a FOR loop of a program, when a DO ... DOEND phrase follows TEMPSTAT, status is restored when the DOEND, BREAK, or GOTO is encountered.

Alternatives to GOTO Statement

While GOTO makes it easy to branch within a program, frequent use of it can obscure the logic of your program, making it difficult to follow its flow, particularly when you have a complex program with several labels and GOTO statements that skip over large portions of code.

To keep the logic of your programs clear, minimize your use of GOTO.

Sometimes a GOTO statement is the best programming technique, but often there are better alternatives. For example:

• Instead of using GOTO statements in a FOR statement, you can often place your alternative sets of statements between DO ... DOEND statements within an IF...THEN...ELSE command itself.

• When each set of statements is long or you want to use them in multiple places in your program, then you might consider placing them in subprograms. Then, you can use an IF...THEN...ELSE command to choose between two different programs, or use a SWITCH command to choose among many different programs.

Example 9-137, "Using a FOR Statement for Looping Over Values" illustrates how the FOR command loops over values. Example 9-138, "Using DO/DOEND in a FOR Loop" illustrates using DO ... DOEND within a FOR loop.

Examples

DEFINE flexrpt PROGRAM
PROGRAM
IF NOT INLIST('East\nWest\nCentral', UPCASE(ARG(1)))
   THEN GOTO argerror
 
SWITCH &UPCASE(ARG(1))
DO
CASE 'EAST':
   ..." (statement group 1)
   BREAK
CASE 'WEST':
   ... "(statement group 2)
   BREAK
CASE 'CENTRAL':
   ..." (statement group 3)
   BREAK
DOEND
 
argerror:
   ..." statements to handle error)
   
END