如果...那么... ELSE-功能

IF THEN ELSE 也可以像函数一样使用来返回单个值。这很像 C 的三元 ? 算子。

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".

使用括号可以简化这样的代码的可读性。

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 的值必须具有相同的数据类型。在这种情况下，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 语句中进行几个比较：

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.