IF THEN ELSE Value Expression



“IF” [[valExpr]] “THEN” [[valExpr]] “ELSE” [[valExpr]] “FI”


IF expr1 THEN expr2 ELSE expr3 FI

The type of expr1 must be Boolean. The type of expr2 must be equal to the type of expr3.

The expressions expr2 and expr3 are only evaluated after the value of expr1 is evaluated to True or False, respectively. For Boolean expressions in which the order of evaluation is irrelevant, one could consider the equivalent alternatives:

  • (expr1 => expr2) /\ (not(expr1) => expr3) or

  • (expr1 /\ expr2) \/ (not(expr1) /\ expr3)