The TRN_MODULE Structure

A structure of type TRN_MODULE contains transformation module information, which represents the simplest form of 1-stage transformation without associated classification information. More complex transformations may be built up by joining several of these modules together, as is done in the MODULE_ARRAY component of a TRN_TRANSFORM structure. The TRN_MODULE structure is defined as follows:

Components of a TRN_MODULE Structure
Component Name	HDS Type	Typical Value	Optional?
NVAR_IN	_INTEGER	2	no
NVAR_OUT	_INTEGER	2	no
COMMENT	_CHAR	`2-d Cartesian --> 2-d Polar'	yes
PRECISION	_CHAR	`_REAL:'	no
FORWARD_FUNC()	_CHAR	`R=SQRT(X*X+Y*Y)',`THETA=A...'	no
INVERSE_FUNC()	_CHAR	`X=R*COS(THETA)',`Y=R*SIN(...'	no

The structure components have the following meanings and restrictions:

NVAR_IN

is a mandatory scalar _INTEGER component with a positive value specifying the number of input variables for the transformation which the module describes.

NVAR_OUT

is a mandatory scalar _INTEGER component with a positive value specifying the number of output variables for the transformation which the module describes.

COMMENT

is an optional scalar _CHAR component of arbitrary length which contains a comment associated with the transformation module. This comment should describe (in English) the type of transformation the module performs. The contents of the COMMENT component are only intended to be human-readable and should not be machine-processed, except that the special three-character sequences `-->' and `<--' (if present) may be automatically interchanged to reflect the effect of inverting the transformation module.

PRECISION

is a mandatory scalar _CHAR component of arbitrary length which contains a valid precision specification for the transformation module, according to the syntax described in Section .

FORWARD_FUNC()

is a mandatory 1-dimensional _CHAR array, with elements of arbitrary length, containing transformation functions which define the forward mapping (according to the syntax in Appendix ). The number of array elements must match the value stored in the NVAR_OUT component.

INVERSE_FUNC()

is a mandatory 1-dimensional _CHAR array, with elements of arbitrary length, containing transformation functions which define the inverse mapping (according to the syntax in Appendix ). The number of array elements must match the value stored in the NVAR_IN component.