Re: [Bug-apl] A few problems

Tue, 05 Feb 2019 09:40:15 -0800



On 02/04/2019 09:13 PM, vvs wrote:
On Mon, Feb 4, 2019 at 2:04 PM Dr. Jürgen Sauermann
<mail@jürgen-sauermann.de> wrote:

Attempting to solve a not decidable problem at runtime is nothing
that I would dare to try.

Well, it seems that it all depends on implementation. While Dyalog
implemented assignment the same way as GNU APL, in NARS2000 it's very
different: all assignments are always treated as variables even if
function with the same name exists. I've tried this:
   ∇A
[1] A←0
∇

   )FNS
A
   )VARS
   A←1
   A
1
   )FNS
   )VARS
A
To me this looks like an undesirable side effect of a parser optimization
(you can collapse 2 Token Z and ← into a single Token Z← instead of parsing
2 Token at runtime). But one can easily construct examples where the results are different.

It also raises the following question:

∇Z←A
 Z←42
∇

A←5

A

What is A and why so? And its is definitely not ISO which says (page 67):
...
If V is a variable-name,
If the current-class of V is nil or variable,
Set the current-referent of V to a token whose class is variable and whose
content is the content of B.
Return a token whose class is committed-value and whose content is B.
Otherwise, signal syntax-error.

/// Jürgen

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