Expressions

 

Each of the three broad type classes has its own set of intrinsic (in-built) operators, these are combined with operands to form expressions. Expressions are made from one operator (eg, +, -, *, /, // and **) and at least one operand. Operands are also expressions.

Expressions have types derived from their operands; they are either of intrinsic type or a user defined type. For example,

• NumBabiesBorn+1 -- numeric valued
• "Ward "//Ward -- character valued
• TimeSinceLastBirth .GT. MaxTimeTwixtBirths -- logical valued

In addition to the intrinsic operations:

• operators may be defined by the user, for example, .INVERSE.. These defined operators (with 1 or 2 operands) are specified in a procedure and can be applied to any type or combination of types. The operator functionality is given in a procedure which must then be mentioned in an interface block. Such operators are very powerful when used in conjunction with derived types and modules as a package of objects and operators.
• intrinsic operators may be overloaded; when using a derived type the user can specify exactly what each existing operator means in the context of this new type.

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