### 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.

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