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
