IF…THEN…ELSE Instructions

The examples of IF…THEN…ELSE instructions in previous chapters demonstrate the two-choice selection. In a flow chart, this appears as follows:

dfhrx001

As a REXX instruction, the flowchart example looks like:
IF expression THEN instruction
              ELSE instruction
You can also arrange the clauses in one of the following ways to enhance readability:
    IF expression THEN
       instruction
    ELSE
       instruction

or

    IF expression
      THEN
        instruction
      ELSE
        instruction
When you put the entire instruction on one line, you must use a semicolon before the ELSE to separate the THEN clause from the ELSE clause.
IF expression THEN instruction; ELSE instruction
Generally, at least one instruction should follow the THEN and ELSE clauses. When either clause has no instructions, it is good programming practice to include NOP (no operation) next to the clause.
IF expression THEN
   instruction
ELSE NOP
If you have more than one instruction for a condition, begin the set of instructions with a DO and end them with an END.
IF weather = rainy THEN
   SAY 'Find a good book.'
ELSE
   DO
     PULL playgolf     /* Gets data from input stream */
     If playgolf='YES' THEN SAY 'Fore!'
   END

Without the enclosing DO and END, the language processor assumes only one instruction for the ELSE clause.


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Timestamp icon Last updated: Tuesday, 7 January 2014


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