Expressions

An expression is a value (a constant, a predefined constant, a variable or the result of a function), which may optionally be preceded by certain operators depending on the type of value, followed by an operator and another value, and so on.

For numeric expressions:

number : a standard number

constant : a constant that represents a numeric value

numeric function : a user-defined or /wiki/cat/intrinsic that returns a numeric value

operator : any of the standard [/cat/arithop|arithmetic operators] ( + - * / ^ \ lang/div lang/mod plus AND OR or XOR)

numeric variable : any variable whose value is a number

For string expressions:

string : a set of zero or more characters surrounded by "

string constant : a predefined constant that represents a string value

string function : a user-defined or /wiki/cat/intrinsic that returns a string value

string variable : any variable whose value is a string

& : indicates that the string value to the right of the ampersand is to be concatenated to the end of the value to the right of the ampersand

For boolean expressions:

NOT : using NOT before a boolean value reverses the value

TRUE or FALSE : the standard boolean constants

numeric constant : a /wiki/cat/number|standard number which will be resolved to either TRUE or FALSE^[1]

boolean constant : a /wiki/cat/constant|predefined constant that represents a boolean value

boolean function : a user defined or /wiki/cat/intrinsic that returns TRUE or FALSE or resolves to TRUE or FALSE^[1]

boolean variable : any variable whose value is TRUE or FALSE or resolves either to TRUE or FALSE^[1]

boolean operator: AND OR XOR = <> < > <= >=

Note that if the expression consists of a number with the operator AND, OR, or XOR followed by a number, it will be treated as an arithmetic expression rather than a boolean expression. At least one of the values in the expression must be a boolean value to produce a boolean expression.

^[1]Note that a /wiki/cat/number, /wiki/cat/constant|predefined constant, /wiki/cat/arith|arithmetic function or numeric variable may be used as a boolean value. If the value of a number, numeric constant, numeric function, or variable is used in a boolean expression is zero, it resolves to FALSE ; all other numeric values used in a boolean expression resolve to TRUE.

See also