-Invalid fields are skipped in iterations. Thus if variable BLOBB is a list -that consists of 3 line, 2 arc and a layer objects, the following assert -will result in 2 comparisons only: +Invalid fields evaluate to value void (and is not considered an error). +Thus if variable BLOBB is a list +that consists of 3 line, 2 arc and a layer objects, the following expression +will be void (false) for at least the 3 line objects and can be true +for at most 2 cases (the arc objects):
(BLOBB.p.width >= 10 mm)-(because only arc objects have valid .p.width field). +(because only arc objects have valid .p.width field, which is the horizontal +radius of an arc).
-An invalid field in an expression is never considered an -error. In an assert statement it causes skipping an iteration. In a -search statement it evaluates to void. - -
A void value is never equal to anything. A void value is not equal even to another void value.