Language basics / Flow control |
The IF instruction executes a group of statements conditionally.
IF condition THEN statement [...] [ ELSE statement [...] ] END IF
If condition is TRUE, the runtime system executes the block of statements following the THEN keyword, until it reaches either the ELSE keyword or the END IF keywords and resumes execution after the END IF keywords.
If condition is FALSE, the runtime system executes the block of statements between the ELSE keyword and the END IF keywords. If ELSE is absent, it resumes execution after the END IF keywords.
By default, the runtime system evaluates all part of the condition. The semantics of boolean expressions can be controlled by the OPTIONS SHORT CIRCUIT compiler directive, to reduce expression evaluation when using AND / OR operators.
A NULL expression is considered as FALSE. Use the IS NULL keyword to test if an expression is null.
MAIN DEFINE name CHAR(20) LET name = "John Smith" IF name MATCHES "John*" THEN DISPLAY "The name starts with [John]!" ELSE DISPLAY "The name is " || name || "." END IF END MAIN