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From: | Elias Mårtenson |
Subject: | Re: [Bug-apl] Floating-point random number function |
Date: | Fri, 30 Jun 2017 12:24:34 +0800 |
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
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