Per the Alf 1.1 specification, a sequence reduction expression is given a multiplicity lower bound of 1. However, if the input sequence to such an expression is null, then the result will be null. Thus, the multiplicity lower bound of the expression should really be 0 (unless, perhaps, the multiplicity lower bound of the input sequence is known to be greater than 0).
seidewitz
commented
6 years ago
Per the Alf 1.1 specification, a sequence reduction expression is given a multiplicity lower bound of 1. However, if the input sequence to such an expression is null, then the result will be null. Thus, the multiplicity lower bound of the expression should really be 0 (unless, perhaps, the multiplicity lower bound of the input sequence is known to be greater than 0).