Selective assignment bug

[Mr. Brian B. McGuinness]

I was trying examples of APL code from the book "APL2 At a Glance" in order to become more familiar with APL2 features.  I found an example that doesn't work.

      ]BOXING 8

      SA←10 'ABC' (3 3⍴⍳9) 20 (5 6)

      SA

┌→────────────────────────┐

│10 ┌→──┐ ┌→────┐ 20 ┌→──┐│

│   │ABC│ ↓1 2 3│    │5 6││

│   └───┘ │4 5 6│    └───┘│

│         │7 8 9│         │

│         └─────┘         │

└∊────────────────────────┘

      ,2 2↑3⊃SA

┌→──────┐

│1 2 4 5│

└───────┘

So far, so good.  But when I try the selective assignment I get

      (,2 2↑3⊃SA)←'WXYZ'

      SA

┌→──────────────────┐

│10 ┌→──┐ Z 20 ┌→──┐│

│   │ABC│      │5 6││

│   └───┘      └───┘│

└∊──────────────────┘

when according to the book I should get

┌→────────────────────────┐

│10 ┌→──┐ ┌→────┐ 20 ┌→──┐│

│   │ABC│ ↓W X 3│    │5 6││

│   └───┘ │Y Z 6│    └───┘│

│         │7 8 9│         │

│         └─────┘         │

└∊────────────────────────┘

which is what I would expect.

I hope that this information proves useful. 

I am having fun experimenting with GNU APL and exploring APL2 features.