Hi Jürgen,
thank you for the details.
for -1- : I thought so. Just making sure.
for -2-: Digging deeper into F12 :
/2 2 ⍴'abcd'
SYNTAX ERROR+
/2 2⍴'abcd'
^
⍝ Should the SYNTAX ERROR not being reported before calling F12?
F12 /0 0 ⍴'abcd'
eval_ident_Bx() called
F12 /1 1 ⍴'abcd'
a
F12 /2 2 ⍴'abcd'
eval_AB() called eval_AB() called
Regarding an e.g. more elaborate F12 function, ****
*eval_ident_Bx() *and *eval_fill_B()* are functions that the interpreter
does not have to (or should not) call.
If F12 gets invoked, the contents of* Value_P A, B, X * is telling F12
how/what to process.
Any kind of side effect (dimentioness, emptiness..) " coming from *A, B
*or*X* has to be handled by F12 internally.
Is this correct?
Best Regards
Hans Peter ****
On 01/03/2026 18:35, Dr. Jürgen Sauermann wrote:
Hi Hans-Peter,
see below.
On 3/1/26 17:49, Hans-Peter Sorge wrote:
Hi Jürgen,
-for 1- In file native/template.hhthe comment states:
// mandatory functions
....
static Token *eval_fill_B*(Value_P B, const NativeFunction * caller);
However there is a fill function for argument B in template_f0:
#if defined TEMPLATE_F0
...
get_function_mux(const char * function_name)
{
....
if (!strcmp(function_name, "*eval_fill_B*"))
return reinterpret_cast<void *>(&*eval_fill_B*);
....
Compile without * if ... eval_fill_B .. * is OK
-for 2- in src/ScalarFunction.cc
it says
/* *eval_fill_B()* is called for:
1. a monadic scalar function with empty B, or ...
...
The Qs:
-1- F0 is niladic. What are the circumstances that *eval_fill_B()*
could get called?
Supposedly never. The *function_mux()* of the native function maps a
function
name string like *"eval_fill_B"*) to a function pointer like
*eval_fill_B()* that can
be called.
To keep things simple, the *function_mux()* is independent of the
arity of the function.
fill functions are either monadic or dyadic, therefore niladic
functions don't have one.
One could remove the calls to *eval_fill_B()* and *eval_fill_AB()* in
the *get_function_mux()
*in *template.hh* but then you have different function_muxed for
different arities which
is merely complicating matters without an obvious advantage.
-2- A monadic call to F12('lib_template_F12.so' ⎕FX 'F12')
with an empty B does not call *eval_fill_B(). *Why not?
F12 'b'
eval_B() called
⍝ as expected
F12 ⍬
eval_B() called
⍝ *eval_fill_B() called* expected too
No The eval_Fill_B function is not called for any empty B but only for
empty arguments of particular functions (most prominently for reduction or
scan of functions with empty arguments). The IBM APL2 reference manual
contains a list of functions and operators for which the fill
functions are
being called.
I suppose that *F12 / ⍬* will say that the fill function was called.
What am I missing?
Best Regards
Hans-Peter
