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

[Christian Robert]

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 
> <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 <address@hidden <mailto:address@hidden> 
> <mailto: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