@Override
    public boolean equals(Object obj) {
        return super.equals(obj) && obj instanceof ChoiceExpression;
    }
An expression which returns the value of the first of a list of subexpressions which
returns a non-null value.

Syntax: sub-expression1 || sub-expression2 || ...

@author bratseth
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ChoiceExpression.java