When writing application programs, you often need to formulate conditions. These are used mostly in control structures , or serve to decide whether to exit a processing block. Conditions use logical expressions that may be either true or false.
Note: Since Release 6.10 it is possible to use not only data objects but also return values of built-in functions and function methods at the operand positions of logical expressions.
Logical expressions can be used as comparisons in the form:
... operand1 operator operand2 ...
Depending on which data type the operands operand1 and operand2 are, different logical relational operators can be used.
Along with operand comparisons, you can formulate logical expressions that check whether the operands meet certain requirements :
Several logical expressions can be linked with a condition.