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

[Elias Mårtenson]

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> 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@hiddentl.ca>> 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>                                                   54.55782413 ┃
        ┃  0.4543486424           ┏→━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓┃
        ┃                         ┃2.024528001 <tel:2.024528001> 2.772781338 ┏→━━━━━━━━━━━━━━━━━━━━━━┓┃┃
        ┃                         ┃                        ↓3.185551114 <tel:3.185551114> 3.13571477 ┃┃┃
        ┃                         ┃                        ┃1.204617876 4 <tel:204617876%204>.396324338┃┃┃
        ┃                         ┃                        ┗━━━━━━━━━━━━━━━━━━━━━━━┛┃┃
        ┃                         ┗∊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛┃
        ┃634.0902523                                                      9.353801479┃
        ┗∊∊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛

        Regards,
        Elias