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# Operator

is a symbol or symbols denoting an operation in an expression or formula:

### Simple

`+` (addition), `-` (subtraction), `*` (multiplication or product), `/`  (division or nesting), `.` (interaction), `=` (assignment), `<` (less than), `>`  (greater than)

### Compound

`**` (exponentiation), `*+` (matrix multiplication), `-*` (crossed deletion), `-/` (nested deletion), `//` (pseudo-term linkage), `.EQ.` or `==` (equality), `.NE.` or `/=` or (non-equality), `.LE.` or `<=` (less than or equal to), `.GE.` or `>=` (greater than or equal to), `.LT.` (less than), `.GT.` (greater than), `.EQS.` (string equality), `.NES.` (string non-equality), `.IN.` (set inclusion), `.NI.` (set non-inclusion), `.IS.` (identifier equivalence), `.ISNT.` (identifier non-equivalence), `.AND.` (logical and), `.OR.` (logical or), `.EOR.` (logical either or), `.NOT.` (logical not).

Only` + - * / . -/ -* `and` // `may occur in formulae, while` . -* -/ `and` // `cannot occur (as operators) in expressions.

### Precedence

The list below shows the order in which the operators are evaluated when they are used in expressions, if brackets are not used to make the order explicit:

(1)                                                 `.NOT.` Monadic `-`

(2)                                                 `.IS. .ISNT. .IN. .NI. *+`

(3)                                                 `**`

(4)                                                 `* /`

(5)                                                 `+` Dyadic `-`

(6)                                                 ` == = /= .LT. .GT. .EQ. .LE. .GE. .NE. .NES.`

(7)                                                 `.AND. .OR. .EOR.`

(8)                                                 `=`

(Monadic minus means the use of the minus sign in a negative number: for example, -1.) Within each class, operations are done from left to right within a expression, unless brackets are used to indicate some other order.

Updated on February 25, 2019