description: This manual page describes both the SDDS_Logic function (which is rarely used by
applications) and, more importantly, the method by which selection logic is applied for
SDDS_SetColumnsOfInterest and SDDS_SetRowsOfInterest.
previous: A logical value resulting from a previous logical operation or from an initial
condition. As usual in C, non-zero is true and zero is false.
match: A logical value resulting from a new matching or selection operation, e.g.,
matching to a wildcard string or comparing to a numerical selection window.
logic: A bitwise combination of the following constants, defined in SDDS.h:
SDDS_NEGATE_MATCH: Indicates that the logical value of match should be
negated (or inverted). This would correspond, for example, to asking that a string
not match a wildcard sequence or that a value be outside a numerical selection
window.
SDDS_NEGATE_PREVIOUS: Indicates that the logical value of previous should
be negated (or inverted).
SDDS_AND, SDDS_OR: One or fewer of these may be specified. If neither is
specified, the value of previous is ignored. Otherwise, the indicated logical operation
is performed with the previous and match values, subject to prior negation as per
the last two items.
SDDS_NEGATE_EXPRESSION: Indicates that the resultant logical value of the
previous three steps should be negated.
return value: Returns 1 one if the result is true, 0 if false.