These predicate functions perform various object comparisons and either succeed returning a null string or cause statement failure. Any of these functions can be redefined by the user.
DIFFER(a,b) succeeds only if a and b are not identical. Copies of strings and integers with equal values are considered identical. For other data types, the two arguments must return a reference to the same instance of that data type to be considered identical.
IDENT(a,b) succeeds only if a and b are identical. Copies of strings and integers with equal values are considered identical. For other data types, the two arguments must return a reference to the same instance of that data type to be considered identical.
LGT(a,b) succeeds if string a is lexically greater than string b. The collating sequence followed is available in &ALPHABET. If one string is shorter than the other, and the shorter string is the initial substring of the longer string, then the longer string is lexically greater than the shorter string.
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