Re: APL lambda question

[Dr . Jürgen Sauermann]

    Hi Henrik,
    
    I believe I fixed the Segfault. You should now get 
    a DEFN ERROR instead with )MORE information.
    SVN 1782.
    
    The reason is this:
    
    1, Conditionals, i.e. COND →→ IFSTAT ←→ ELSESTAT ←←
        create 2 or 3 statements, one for COND, one for IFSTAT and
        optionally one for ELSESTAT.
    
    2. GNU APL lambdas are limited to one APL _expression_ (= one APL
    statement)
       and the _expression_ must yield a value (and can therefore not be a
    branch).
    
    3. The normal work-around for this limitation is to use a proper
    ∇-defined function.
    
    Best Regards,
    Jürgen

On 10/23/24 21:16, Henrik Moller wrote:

Gave it a try:

     x←6
     y←⍳5  
     (2=⎕nc'x') →→ x⍴y ←→ ⍴y ←←
1 2 3 4 5 1
     )erase x
     (2=⎕nc'x') →→ x⍴y ←→ ⍴y ←←
5
     tryit←{(2=⎕nc'x') →→ x⍴y ←→ ⍴y ←←}


===================================================
SEGMENTATION FAULT
*** useless apl.lines (no CXXFLAGS=-rdynamic -gdwarf-2)

----------------------------------------
-- Stack trace at main.cc:102
----------------------------------------
0x7fd5887171e2 __libc_start_main
0x485c8a  main
0x63dd25   Workspace::immediate_execution(bool)
0x4ef575    Command::process_line()
0x4efbe1     Command::finish_context()
0x4fc307      Executable::execute_body() const
0x5cd5c0       StateIndicator::run()
0x53bb21        Prefix::reduce_statements()
0x53b430         Prefix::push_END_error()
0x536636          Prefix::syntax_error(char const*)
0x4fc0a1           throw_apl_error(ErrorCode, char const*)
0x4fbe3f            Error::update_error_info(StateIndicator*)
0x500770             Executable::set_error_info(Error&, Function_PC2) const
0x7fd588cfd1b0               
0x48b0b7                
========================================
========================================
====================================================


Probably not worth trying to fix this--it's too obscure.



[3] ~tinkering/apl/mtx/src >        

On 10/23/24 12:30, Dr. Jürgen Sauermann wrote:

Hi Hendrik,

as far as I remember: in GNU APL a lambda is pretty much a regular defined function.
A nomadic lambda is simply a dyadic lambda which test for the presence for its left
argument (read: ⎕NC lambda = 2).Tour tryit needs to check that before ⍺ is referenced).

Best Regards,
Jürgen

On 10/23/24 16:55, Henrik Moller wrote:

To all APLers:  In GNU APL, is there any way to define an ambivalent lambda?  I.e., if you define a lambda

tryit←{...}

is there any way to make it work with both

tryit 1

and

1 tryit 2

The Net has been unhelpful...

Thanks