Re: APL2 Compatibility

[Dr . Jürgen Sauermann]

    Hi Jay,
      
      I see, thanks. I was thinking of the table "NAME AND SYMBOL
      BINDING"
      on page 21 and repeated on page 34. It uses the neutral term "left
      operand"
      without being specific whether that operand is a value, a function
      or an operator.
      
      I read the sentence you quote somewhat differently. Not in the
      sense that
      one operator cannot be the left or operand of another operator but
      rather that the
      binding rules concerning operands of operators shall not apply if
      an operand is
      itself an operator. The example that follows wisely excluded the
      case where
      an operator like / could also be evaluated as a function.
      
      I believe the sentence is equivalent to saying, in parser terms,
      that OP OP shall
      be shifted rather than being reduced. That will unfortunately
      create more derived
      functions, but these cases are so rare that that will not matter.
      I will therefore
      see what happens if I remove all parser reductions with adjacent
      operators
      from the phrase table of GNU APL and see if that causes new
      problems
      (I suppose at least some automatic testcases will fail).
      
      Best Regards,
      Jürgen

On 11/30/20 1:25 PM, Jay Foad wrote:

> > My
> >
> > 1 / / 1 1 ⍴ 1
> >
> > example was only meant to demonstrate that in APL2 an operator can have
> > another operator (in this case itself) as left argument. And in that case binding
> > the leftmost 1 to the left / operator would be, at least IMHO and referring only
> > to the language reference manual, as valid as binding the left / operator to the
> > right / operator.
> >       
> I don't think so. See the discussion of "Name and Symbol Binding"
> starting on p33, and in particular on p35:
>
> "There is no binding between operators. In the _expression_ ,¨/ catenate binds as
> left operand to the each operator, and then the derived function ,¨
> binds as left
> operand to the slash operator."
>
> Jay.
>