sub_or_null

arithmetic-functions sub_or_null

syntax

  • sub_or_null(a, b)

definition

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.

applies to

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

conditions

  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

example 

1. attribute<uint8> sub_or_null_AB (ADomain) := sub_or_null(A, B);
A B sub_or_null_AB
0 1 null
1 null null
200 54 146
50 100 null
222 111 111

ADomain, nr of rows = 5

see also

work-around with backward compatibility for numeric overflow issues after GeoDMS 14.1.0

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');