Re: [Bug-apl] Floating-point random number function

[Christian Robert]

You are right !

Xtian.

On 2017-06-30 16:48, Frederick Pitts wrote:
> Xtian,
>
>         Actually the function you present returns the type of the
> argument, not the prototype, as per
>
>                 Type <=> ↑0ρ⊂R
>
> on page 46 of IBM's "APL2 Programming: Language Reference".  The
> prototype is the type of the first element of R, i.e.,
>
>                 Prototype <=> ↑0⍴⊂↑R
>
> Regards,
>
> Fred
>
> On Fri, 2017-06-30 at 00:33 -0400, Christian Robert wrote:
> > I don't know, your "(res+V×0)" is probably the way to go for that
> > purpose, I'm not an expert but I understand what you mean.
> >
> > I have an alias defined as:
> >
> >      proto←{↑0⍴⊂ ⍵}
> >
> > that give me the prototype of the argument (use with: 24 QuadCR proto
> > w). It will probably not help you but good to know.
> >
> >
> > Xtian.
> >
> > On 2017-06-30 00:24, Elias Mårtenson wrote:
> > > The purpose of it is to preserve the structure of the argument,
> > > while setting all values to MAXINT.
> > >
> > > Is there a better way to achieve this?
> > >
> > > Regards,
> > > Elias
> > >
> > > On 30 June 2017 at 12:21, Christian Robert <address@hidden
> > > l.ca <mailto:address@hidden>> wrote:
> > >
> > >      On 2017-06-30 00:19, Elias Mårtenson wrote:
> > >
> > >          Thanks. I'll stick with this for now then.
> > >
> > >          How would (res+V×0) wrap around, by the way?
> > >
> > >
> > >      Bad first reading, (res+V×0) does nothing, it add 0 to "res".
> > > How is it usefull ?
> > >
> > >      Xtian.
> > >
> > >
> > >
> > >          On 30 June 2017 at 12:17, Christian Robert <christian.rober
> > > address@hidden <mailto:address@hidden> <mailto:christian
> > > address@hidden <mailto:address@hidden>>> wrote:
> > >
> > >               I think this is the best you can get, about 62 bits of
> > > randomness.
> > >
> > >                      (64⍴2) ⊤⎕syl[20;2] ⍝ the largest 64 bits
> > > integer supported by gnu-apl
> > >               0 1 1 1 1 1 1 1 1 0 1 0 1 1 0 0 1 1 1 1 0 1 1 1 0 1 0
> > > 0 0 0 0 1 1 0 0 1 1 1 0 1 1 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> > > 0 0 0
> > >
> > >               so, it's a bit less than 63 bits, say 62 bits for
> > > safety is Ok.
> > >
> > >               Note that (res+V×0) may wrap around.
> > >
> > >               Xtian.
> > >
> > >               On 2017-06-29 23:23, Elias Mårtenson wrote:
> > >
> > >                   I had a need to have a function that does the same
> > > as monadic ?, but with the difference that the resulting numbers
> > > not be integers, but floating point.
> > >
> > >                   Now, here's my attempt at creating such a
> > > function, I'd like to know if this is the best way to achieve what
> > > I need:
> > >
> > >                   ∇ r←*hrRand* V ;res
> > >                       ⍝⍝ Like monadic ?, but returns floating point
> > > numbers
> > >                       res ← ⎕SYL[19+⎕IO;1+⎕IO]
> > >                       r ← V × res÷⍨ ?res+V×0
> > >                   ∇
> > >
> > >                   Example:
> > >
> > >                   *      hrRand 3 2 ⍴ 10 100 5 (3 4 (2 2⍴5)) 1000*
> > >                   ┏→━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
> > > ━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
> > >                   ↓ 4.138685128 <tel:4.138685128> <tel:4.138685128
> > > <tel:4.138685128>>
> > >    54.55782413 ┃
> > >                   ┃  0.4543486424           ┏→━━━━━━━━━━━━━━━━━━━━━━
> > > ━━━━━━━━━━━━━━━━━━━━━━━━━━┓┃
> > >                   ┃                         ┃2.024528001
> > > <tel:2.024528001> <tel:2.024528001 <tel:2.024528001>> 2.772781338
> > > ┏→━━━━━━━━━━━━━━━━━━━━━━┓┃┃
> > >                   ┃                         ┃
> > >   ↓3.185551114 <tel:3.185551114> <tel:3.185551114 <tel:3.185551114>>
> > > 3.13571477 ┃┃┃
> > >                   ┃                         ┃
> > >   ┃1.204617876 4 <tel:1.204617876%204>
> > > <tel:204617876%204>.396324338┃┃┃
> > >                   ┃                         ┃
> > >   ┗━━━━━━━━━━━━━━━━━━━━━━━┛┃┃
> > >                   ┃                         ┗∊━━━━━━━━━━━━━━━━━━━━━━
> > > ━━━━━━━━━━━━━━━━━━━━━━━━━━┛┃
> > >                   ┃634.0902523
> > >                  9.353801479┃
> > >                   ┗∊∊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
> > > ━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
> > >
> > >                   Regards,
> > >                   Elias