Language Reference

IEEE Derived Data Types and Constants

The IEEE modules define the following derived types.

IEEE_FLAG_TYPE

A derived data type defined by the IEEE_EXCEPTIONS module that identifies a particular exception flag. The values for IEEE_FLAG_TYPE must be one of the following named constants as defined in the IEEE_EXCEPTIONS module:

IEEE_OVERFLOW

Occurs when the result for an intrinsic real operation or an assignment has an exponent too large to be represented. This exception also occurs when the real or imaginary part of the result for an intrinsic complex operation or assignment has an exponent too large to be represented.

When using REAL(4), an overflow occurs when the result value's unbiased exponent is > 127 or < -126.

When using REAL(8), an overflow occurs when the result value's unbiased exponent is > 1023 or < -1022.

IEEE_DIVIDE_BY_ZERO

Occurs when a real or complex division has a nonzero numerator and a zero denominator.

IEEE_INVALID

Occurs when a real or complex operation or assignment is invalid.

IEEE_UNDERFLOW

Occurs when the result for an intrinsic real operation or assignment has an absolute value too small to be represented by anything other than zero, and loss of accuracy is detected. The exception also occurs when the real or imaginary part of the result for an intrinsic complex operation or assignment has an absolute value that is too small to be represented by anything other than zero, and loss of accuracy is detected.

For REAL(4), an underflow occurs when the result has an absolute value < 2^-149.

For REAL(8), an underflow occurs when the result has an absolute value < 2^-1074.

IEEE_INEXACT

Occurs when the result of a real or complex assignment or operation is not exact.

The following constants are arrays of IEEE_FLAG_TYPE:

IEEE_USUAL

An array named constant containing IEEE_OVERFLOW, IEEE_DIVIDE_BY_ZERO, and IEEE_INVALID elements in order.

IEEE_ALL

An array named constant containing IEEE_USUAL, IEEE_UNDERFLOW, and IEEE_INEXACT elements in order.

IEEE_STATUS_TYPE

A derived data type defined in the IEEE_ARITHMETIC modules that represents the current floating-point status as defined in the IEEE_ARITHMETIC module. The floating-point status encompasses the values of all exception flags, halting, and rounding modes.

IEEE_CLASS_TYPE

A derived data type defined in the IEEE_ARITHMETIC module that categorizes a class of floating-point values. The values for IEEE_CLASS_TYPE must be one of the following named constants as defined in the IEEE_ARITHMETIC module:

IEEE_ROUND_TYPE

A derived data type defined in the IEEE_ARITHMETIC modules that identifies a particular rounding mode. The values for IEEE_ROUND_TYPE must be one of the following named constants as defined in the IEEE_ARITHMETIC module:

IEEE_NEAREST

Rounds the exact result to the nearest representable value.

IEEE_TO_ZERO

Rounds the exact result to the next representable value, towards zero.

IEEE_UP

Rounds the exact result to the next representable value, towards positive infinity.

IEEE_DOWN

Rounds the exact result to the next representable value, towards negative infinity.

IEEE_OTHER

Indicates that the rounding mode does not conform to the IEEE standard.

IEEE_FEATURES_TYPE

A derived data type defined in the IEEE_FEATURES module that identifies the IEEE features to use. The values for IEEE_FEATURES_TYPE must be one of the following named constants as defined in the IEEE_FEATURES module: