sub_or_null - ObjectVision/GeoDMS GitHub Wiki

Arithmetic functions sub_or_null

• sub_or_null(a, b)

sub_or_null(a, b) results in the element-by-element subtraction of corresponding values of the data items: a and b. If the result of the addition exceeds the MinValue or MaxValue of the value type, the sub_or_null function results in the value null.

Data items with Numeric, Point, or String value type.

1. Domain units of the arguments must match or be void, (literals or parameters can be added to data items of any domain).
2. Arguments must have matching:
   • value type
   • metric

1. attribute<uint8> sub_or_null_AB (ADomain) := sub_or_null(A, B);

ADomain, nr of rows = 5

• sub

Old situation giving numeric overflow issues:

attribute<string> prev_name  := MakeDefined(name[id(.) -1b], 'StartingYear');

With the new sub_or_null() operator:

attribute<string> prev_name  := MakeDefined(name[sub_or_null(id(.),1b)], 'StartingYear');

Preferred backwards compatible option:

attribute<string> prev_name  := id(.) >= 1b ? name[id(.) - min_elem( id(.), 1b)] : 'StartingYear';

Alternative, which looks more like the old one:

attribute<string> prev_name  := 
   MakeDefined(name[id(.) >= 1b ? id(.) - min_elem(id(.), 1b) : 0b/0b], 'StartingYear');