Ah, that all makes sense. I hadn't considered the differing return types
for )ERASE vs. ⎕EX, that is useful.
Thank you,
-Russ
On Sat, 10 Jul 2021 at 07:05, Dr. Jürgen Sauermann <mail@jürgen-sauermann.de>
wrote:
> Hi,
>
> I believe this is simply a misunderstanding of functionality.
>
> Consider this (something similar happens if you )COPY the same script
> twice):
>
> * )CLEAR**
> ** FOO←{ 42 ⊣ ⍵ } ⍝ OK: create monadic defined function FOO
> (which returns 42)**
> ** FOO←{ 42 ⊣ ⍵ } ⍝ ERROR: FOO is now a defined function, so you
> cannot assign anything to it.**
> **SYNTAX ERROR**
> ** FOO←λ1**
> ** ^ ^*
>
> As matter of protection, in GNU APL you cannot re-define a named lambda
> without erasing it.
> You can (and in most cases should), however, localize it.
>
> As to )ERASE vs. ⎕EX: use )ERASE in immediate execution mode (preferably
> after )SIC)
> and ⎕EX in defined functions. In immediate execution (which includes
> scripts) it is a matter
> of preference which one you use and in which fashion you want to get the
> success of the of
> the operation (error text for failed )ERASE or a boolean vector for ⎕EX).
>
> Best Regards,
> Jürgen
>
>
> On 7/10/21 6:41 AM, Russtopia wrote:
> > I have noticed what I believe are some inconsistencies (bugs?) with
> > how GNU APL handles reloading/overwriting/erasing of symbols which are
> > 'trad fns' versus 'lambda fns'.
> >
> > Consider the following )DUMP file:
> >
> > --8<--
> > #!/usr/local/bin/apl --script
> > ⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝
> > ⍝ ⍝
> > ⍝ sink.apl 2021-07-09 20:04:14 (GMT-8) ⍝
> > ⍝ ⍝
> > ⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝⍝
> >
> > Life←{↑1 ⍵∨.∧3 4=+/,¯1 0 1∘.⊖¯1 0 1∘.⌽⊂⍵}
> >
> > ∇a←MatToVecArray M
> > ⍝⍝ Return rows in M as an array of vectors
> > ⍝⍝ lambda (dfn) version: {(⊂⍺){⍺[⍵;]}¨⍳≢⍵} ⍝⍨M
> > a←{⊂M[⍵;]}¨⍳≢M
> > ∇
> > --8<--
> >
> > The above will )LOAD and )LOAD a second time, without error (as I
> > presume it totally overwrites the current WS). However, )COPY or
> > )PCOPY will give an error for the 'Life' function if it is already
> > loaded into the current WS:
> >
> > )copy sink Life
> > DUMPED 2021-07-09 20:04:14 (GMT-8)
> > )copy sink Life
> > DUMPED 2021-07-09 20:04:14 (GMT-8)
> > SYNTAX ERROR
> > Life←λ1
> > ^ ^
> >
> > Regular 'trad fns' can be re-loaded into the current WS without issue.
> >
> > If I add in
> >
> > ⎕EX 'Life'
> >
> > to sink.apl above the definition, )COPY and PCOPY will now succeed;
> > but if I )DUMP this WS back to file, the ⎕EX is not part of the )DUMP
> > output so problems will re-occur.
> >
> > As an final note, as an APL newcomer: When is it preferable to use ⎕EX
> > instead of )ERASE ?)
> >
> > Thanks,
> > -Russ
> >
>
>
