![]() This allows you to avoid unnecessary time-consuming expression evaluations. Any logical expressions to the right of this expression are not evaluated. For example, if there are multiple AND tests, the first expression that returns 0 determines the overall Boolean result. When short-circuit logical operators are used to combine logical expressions, InterSystems IRIS evaluates only as many expressions as are needed to determine the Boolean result. This assures that all expressions are valid. When regular logical operators are used to combine logical expressions, InterSystems IRIS evaluates all of the specified expressions, even when the Boolean result is known before all of the expressions have been evaluated. There are two types of logical operators: regular logical operators (& and !) and short-circuit logical operators (& and ||). ![]() Like all InterSystems IRIS expressions, they are evaluated in strict left-to-right order. You can combine multiple Boolean logical expressions by using logical operators. For further details, refer to String-to-Number Conversion. InterSystems IRIS® evaluates a non-numeric string as having a zero numeric value. Any expression that evaluates to a zero numeric value returns a Boolean 0 (FALSE) value. In a Boolean test, any expression that evaluates to a non-zero numeric value returns a Boolean 1 (TRUE) value. Logical expressions are most commonly used with: They evaluate expressions and result in a Boolean value: 1 (TRUE) or 0 (FALSE). ![]() Logical expressions use logical operators, numeric relational operators, and string relational operators. The simplest expression is simply a literal or variable: x, yĪn ObjectScript expression is one or more tokens that can be evaluated to yield a value. This results in the following logical values, when x and y are different non-numeric strings (for example x=”Fred”, y=”Wilma”). You can prepend the PlusSign property value (+ by default) to force numeric evaluation of a string for example, "+123". Because the equal sign is used for both the numeric equality operator and the string comparison operator, string comparison takes precedence for = and '= operations. For, '>, = comparisons a non-numeric string is also treated as the number 0. If the leading characters of the string are not numeric characters, the string’s numeric value is 0 for all arithmetic operations. The following example shows arithmetic comparisons of numeric strings: Numeric strings are not converted to canonical form prior to equality comparisons (=, '=), because these operators are also used for string comparisons. The right-hand side of an assignment command is an expression: Within ObjectScript the SET command is used along with the assignment operator ( = ) to assign a value to a variable. Some operators take only one operand and are known as unary operators others take two operands and are known as binary operators.Īn operator and any of its operands taken together constitute an expression. When used together, an operator and its associated operands have the following form: Each operand consists of one or more expressions or expression atoms. ![]() Operators are symbolic characters that specify the action to be performed on their associated operands. ![]() Introduction to Operators and Expressions This topic describes expressions and the operators. Operators act on expressions, which are variables or other entities that ultimately evaluated to a value. Indirection supports many different operators, which perform various actions, including mathematical actions, logical comparisons, and so on.Introduction to Operators and Expressions. ![]()
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