That is a language extension specific to MicroAPL. It is not part of either ISO Extended APL or IBM APL 2, which are the references upon which GNU APL is based.
The README-7-more-info file in the GNU APL distribution contains links to the reference documents. On Wed, 2014-05-28 at 20:15 -0700, Akiva Avraham wrote: > I am not experienced enough in gnu-APL to determine whether you intend > for this type of expression to be executable, so I just bring it to > your attention. > > http://www.microapl.co.uk/apl_help/ch_020_020_310.htm > > > If the arguments contain object (or class) references, the elements > are considered equal if the reference indices are the same, i.e. if > they refer to the same entry in APL's internal table of objects. For > internal objects, this will be true if and only if the elements refer > to the same object. Note that different objects which happen to > contain the same properties are not considered equal. For example, if > Point is a simple class with properties X and Y: > > PT←⎕NEW Point > PT.X←63 ⋄ PT.Y←42 > A←PT > B←PT.⎕CLONE 1 > A.⎕DS > X=63, Y=42 > B.⎕DS > X=63, Y=42 > A=PT ⍝ References to the same object > 1 > B=PT ⍝ Objects are different, but have the same property > values > 0 > > For external objects, there might be two references which APL does not > know refer to the same object. Therefore the use of the APL Equals > primitive on external objects is not recommended. > > > > -- >
