The VAL, VEC and NUM Facilities

The routines in this package have names of the form $<$fac$>$_$<$name$>$, where $<$fac$>$ is a three character facility name and $<$name$>$ specifies the operation which the routine performs.

The routines are divided into three facilities as follows:

$<$fac$>$	Facility provides...
VAL	Arithmetic, mathematical functions and type conversion on single (scalar) values. Handling of numerical errors and bad value propagation are incorporated.
VEC	Arithmetic, mathematical functions and type conversion on vectorised arrays, allowing more efficient processing of large numbers of data. Handling of numerical errors and bad value propagation are incorporated.
NUM	Lower level routines for arithmetic, mathematical functions, type conversion and inter-comparison of single numbers. Operations are performed without protection against numerical errors and without regard for bad values.

Note that a distinction is drawn between three classes of primitive data, which differ in their interpretation and in the algorithms best suited to processing them:

• Values (VAL facility) are scalar data which may take one of the Starlink-defined bad values (sometimes called ``magic'' values), whose presence signifies that the affected datum is undefined. Numerical errors which occur while processing values will result in the generation of a bad value as a result. Subsequent recognition of bad values on input may (or may not) occur, depending on the logical setting of the BAD routine argument (section ).

• Vectorised arrays (VEC facility) are 1-dimensional arrays of values (or arrays treated as 1-dimensional) whose elements are processed in the way described above. The routines provided are optimised to perform processing in an efficient manner when the size of the array is large.

• Numbers (NUM facility) are always interpreted literally as scalar numerical quantities (i.e. bad values are not recognised on input and are not explicitly generated on output). Numerical errors which occur while processing numbers will cause the application to terminate (i.e. crash).

Italics are used throughout this document to refer to values, vectorised arrays and numbers when it is important to emphasise the particular meaning (and the implied processing rules) described here.