Re: [Bug-apl] dynamic function not referencing global?

[Christian Robert]

On 2016-10-26 15:04, Juergen Sauermann wrote:
> Hi Xtian,
>
> as I said, in the niladic case it is the APL syntax and not the fact that
> a function is defined as lambda which causes this behavior. Therefore
> local variables have no effect here.
>
> If we would change this then niladic lambdas would behave differently than
> niladic non-lambda functions, which I consider worse than not being
> able to define named niladic lambdas. And such a syntax would deviate from
> the standard APL syntax.
>
> As a matter of fact, all lambdas (niladic or not) are converted to defined 
> functions
> of the same valence long before the statement is executed. It is only in 
> immediate
> execution mode that the niladic function is computed immediately. The same
>  *time←{⎕TS**}* inside another define function, say FOO, may be computed long
> after the FOO is *⎕FX*ed. The conversion of *time←{⎕TS**}* into a niladic 
> defined
> function called *λ1* happens when FOO is ⎕FXed while the resulting *time←***λ1**
> happens later when FOO reaches that statement in FOO.  At that later point in 
> time
> normal vanilla APL execution is taking place, and we do not want to change 
> that, do we?

No, we don't want that !

Xtian.

> /// Jürgen
>
>
>
> On 10/26/2016 08:16 PM, Christian Robert wrote:
> > Niladic Lambda can be usefull.
> >
> > I wonder if it could be possible to use some trick to generate niladic Lambda.
> >
> >
> > Like in:
> >
> >
> >       )erase time
> >
> >       time←{⎕TS ;x}
> >
> > Since this lambda has a local variable defined, then it should be a definition 
> > and since
> >
> > there is no ⍵ nor ⍺ then it should be niladic one.
> >
> > Only Juergen can say if it is possible, or find an other trick and how hard to 
> > implement ...
> >
> > Just some personnal tought.
> >
> > Xtian.
> >
> >
> > On 2016-10-26 06:54, Juergen Sauermann wrote:
> > > Hi,
> > >
> > > correct. To explain why this is so, consider this:
> > >
> > > *     {1+2}**
> > > **3
> > >
> > > **      {1+⍵}**
> > > **SYNTAX ERROR*
> > >
> > > *      {1+⍵} 5**
> > > **6**
> > > *
> > > Therefore in
> > >
> > > *      F0←{1+2}*
> > >
> > > GNU APL first reduces *{1+2} *to *3* and then assigns *3* to *F0*, making *F0* 
> > > a variable
> > > because a values is being assigned to a name. This is normal APL and holds for
> > > all niladic functions and not only for niladic lambdas.
> > >
> > > In contrast, in
> > >
> > > *      F1←**{1+⍵}
> > > *
> > > **{1+⍵}**cannot be reduced (as opposed to *{1+⍵} 5*which can), so it is shifted 
> > > onto
> > > the evaluation stack, then *←* is shifted (still not being able to be reduced), 
> > > and finally
> > > *F1* is shifted. At this point the stack contains the valid phrase 
> > > *F1←**{1+⍵}*, which can
> > > be reduced and causes *F1 *to become a monadic function bound to the name *F1*.
> > >
> > > /// Jürgen
> > >
> > >
> > > On 10/25/2016 07:01 PM, Christian Robert wrote:
> > > > DISPLAYhand←{,(⍪hand),' '}
> > > >
> > > > this create a variable DISPLAYhand
> > > >
> > > > this is because de {} does not contain neither alpha nor omega.
> > > >
> > > > Xtian.
> > > >
> > > >
> > > > On 2016-10-25 12:54, address@hidden wrote:
> > > > > Hi bug-apl,
> > > > >
> > > > > Why does DISPLAYhand not use the new value of hand on the second call?
> > > > >
> > > > >
> > > > >       deck←''
> > > > >       deck←deck,"🂢" "🂲" "🃂" "🃒"
> > > > >       deck←deck,"🂣" "🂳" "🃃" "🃓"
> > > > >       deck←deck,"🂤" "🂴" "🃄" "🃔"
> > > > >       deck←deck,"🂥" "🂵" "🃅" "🃕"
> > > > >       deck←deck,"🂦" "🂶" "🃆" "🃖"
> > > > >       deck←deck,"🂧" "🂷" "🃇" "🃗"
> > > > >       deck←deck,"🂨" "🂸" "🃈" "🃘"
> > > > >       deck←deck,"🂩" "🂹" "🃉" "🃙"
> > > > >       deck←deck,"🂪" "🂺" "🃊" "🃚"
> > > > >       deck←deck,"🂫" "🂻" "🃋" "🃛"
> > > > >       ⍝deck←deck,"🂬" "🂼" "🃌" "🃜"   ⍝knights
> > > > >       deck←deck,"🂭" "🂽" "🃍" "🃝"
> > > > >       deck←deck,"🂮" "🂾" "🃎" "🃞"
> > > > >       deck←deck,"🂡" "🂱" "🃁" "🃑"
> > > > >       deck ← ⊖13 4 ⍴ deck
> > > > >
> > > > >       hand←(∈deck)[13?52]
> > > > >       DISPLAYhand←{,(⍪hand),' '}
> > > > >
> > > > >       DISPLAYhand
> > > > > 🂢 🃈 🃃 🂷 🃞 🃙 🃝 🂫 🃋 🃕 🃒 🃂 🂧
> > > > >       hand←(∈deck)[13?52]
> > > > >       DISPLAYhand
> > > > > 🂢 🃈 🃃 🂷 🃞 🃙 🃝 🂫 🃋 🃕 🃒 🃂 🂧
> > > > >       hand
> > > > > 🂤🂺🂾🂷🂪🂱🂳🂸🃚🃅🂻🂲🂭
> > > > >
> > > > >
> > > > > Thanks,
> > > > > Alex