4.1.7.2 Specification Expressions

A specification expression is a restricted expression that is of type integer and has a scalar value. This type of expression appears only in the declaration of array bounds and character lengths.

In a restricted expression, each operation is intrinsic and each operand is one of the following:

• A constant or subobject of a constant
  
  
• A variable that is one of the following:
  
  
  • A dummy argument that does not have the OPTIONAL or INTENT (OUT) attribute (or the subobject of such a variable)
    
    
  • In a common block (or the subobject of such a variable)
    
    
  • Made accessible by use or host association (or the subobject of such a variable)
  
  
• A structure constructor whose components are restricted expressions
  
  
• An implied-do variable within an array constructor where the bounds and strides of the corresponding implied-do are restricted expressions
  
  
• A reference to one of the following inquiry functions:
  
  

  BIT_SIZE	NWORKERS
  DIGITS	PRECISION
  EPSILON	PROCESSORS_SHAPE
  HUGE	RADIX
  ILEN	RANGE
  KIND	SHAPE
  LBOUND	SIZE
  LEN	SIZEOF
  MAXEXPONENT	TINY
  MINEXPONENT	UBOUND
  NUMBER_OF_PROCESSORS

  Each function argument must be one of the following:

  • A restricted expression
    
    
  • A variable whose properties inquired about are not dependent on the upper bound of the last dimension of an assumed-size array, are not defined by an expression that is not a restricted expression, or are not definable by an ALLOCATE or pointer assignment statement.
  
  
• A reference to any other intrinsic function where each argument is a restricted expression.
  
  
• A reference to a specification function where each argument is a restricted expression
  
  
• An array constructor where each element and the bounds and strides of each implied-do, are expressions whose primaries are restricted expressions
  
  
• Another restricted expression enclosed in parentheses

Each subscript, section subscript, and substring starting and ending point must be a restricted expression.

Specification functions can be used in specification expressions to indicate the attributes of data objects. A specification function is a pure function. It cannot have a dummy procedure argument or be any of the following:

• An intrinsic function
  
  
• An internal function
  
  
• A statement function
  
  
• Defined as RECURSIVE

A variable in a specification expression must have its type and type parameters (if any) specified in one of the following ways:

• By a previous declaration in the same scoping unit
  
  
• By the implicit typing rules currently in effect for the scoping unit
  
  
• By host or use association

If a variable in a specification expression is typed by the implicit typing rules, its appearance in any subsequent type declaration statement must confirm the implied type and type parameters.

If a specification expression invokes an inquiry function for a type parameter or an array bound of an object, the type parameter or array bound must be specified in a prior specification statement (or to the left of the inquiry function in the same statement).

In a specification expression, the number of arguments for a function reference is limited to 255.

Examples

The following shows valid specification expressions:

MAX(I) + J          ! I and J are scalar integer variables
UBOUND(ARRAY_B,20)  ! ARRAY_B is an assumed-shape dummy array

For More Information:

• On array constructors, see Section 3.4.2.4.
  
  
• On implicit typing rules, see Section 3.4.1.2.
  
  
• On structure constructors, see Section 3.2.4.
  
  
• On intrinsic functions, see Chapter 9.
  
  
• On use and host association, see Section 16.4.1.2.
  
  
• On pure procedures, see Section 8.5.1.2.