Intrinsic operators can be extended further by the programmer to operate on operands of types for which there are no intrinsic operations.
Similarly, you can use defined unary and defined binary operators to operate on operands of types for which there are no previous definitions.
Fortran allows the intrinsic operator symbols to be extended to cases in which the operands are not of the usual intrinsic types defined by the standard.
For example, the (a user-defined type) or for operands of type logical with the interpretation provided by a user-supplied function subprogram.
These are user-defined operators, which are either unary or binary operators.
They have the form of a sequence of letters surrounded by periods; are examples of possible user-defined operators.The formation rules for expressions imply that the defined unary operators have highest precedence of all operators, and defined binary operators have the lowest precedence of all operators.When they appear in a context where two or more of these operators of the same precedence are adjacent, the operands are combined with their operators in a left-to-right manner, as is the case for the familiar operates on operands of type integer as well as real and complex.This chapter describes using arrays and pointers in the following contexts: The result obtained from the evaluation of an expression can be used in many ways.For example, it can be printed or passed to a subprogram.As with operators, the programmer can extend the meaning of assignment to types not defined intrinsically and can redefine assignment for two objects of the same derived type. In addition, arrays and pointers each have special forms of assignment statements called masked array assignment and pointer assignment, respectively.These two assignment statement forms are described later in this chapter.The four forms of the assignment statement are also described in this chapter.Note: : The Fortran statement syntax in this manual is defined using the same terms used in the Fortran standard.The rules for construction of expressions (the syntax rules) are the same for user-defined operators as for intrinsic operators.The general rule for evaluation of a Fortran expression states that any method that is mathematically equivalent to that provided by the construction and interpretation rules for the expression is permitted, provided the order of evaluation indicated by explicit parentheses in the expression is followed.