如果...那麼... ELSE-功能

IF THEN ELSE 也可以像函式一樣使用來返回單個值。這很像 C 的三元 ? 運算元。

DEFINE VARIABLE i AS INTEGER     NO-UNDO.
DEFINE VARIABLE c AS CHARACTER   NO-UNDO.

/* Set c to "low" if i is less than 5 otherwise set it to "high"    
c = IF i < 5 THEN "low" ELSE "high".

使用括號可以簡化這樣的程式碼的可讀性。

DEFINE VARIABLE i AS INTEGER     NO-UNDO.
DEFINE VARIABLE c AS CHARACTER   NO-UNDO.

c = (IF i < 5 THEN "low" ELSE "high").

IF-part 的值和 ELSE-part 的值必須具有相同的資料型別。在這種情況下，不可能使用 ELSE IF。

DEFINE VARIABLE dat                AS DATE        NO-UNDO.
DEFINE VARIABLE beforeTheFifth     AS LOGICAL   NO-UNDO.

dat = TODAY.

beforeTheFifth = (IF DAY(dat) < 5 THEN TRUE ELSE FALSE).

可以在 IF 語句中進行幾個比較：

DEFINE VARIABLE between5and10 AS LOGICAL     NO-UNDO.
DEFINE VARIABLE i             AS INTEGER     NO-UNDO INIT 7.

between5and10 = (IF i >= 5 AND i <= 10 THEN TRUE ELSE FALSE).

MESSAGE between5and10 VIEW-AS ALERT-BOX.