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

[Frederick Pitts]

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
> > 
> > 
> >