PARI's commands - Page 218

Batalov · 2013-06-22, 08:02

Quote:

Originally Posted by LaurV

That was a system malfunction... How the programmer decided if the cabbages have eggs? Anyhow, the result is wrong in all cases: if no eggs, he should come with two cabbages. If someone had eggs (the grocery, the cabbage, the seller, whatever), then the guy should return with 14 cabbages...

The seller didn't have eggs... he had balls!

LaurV · 2013-06-22, 08:09

And that is how your world turns upside-down

As a programmer-for-living for few decades, changing my tools many times (sometime few times per year, depending of the projects I was working for) I learned a good lesson: you have to know your tools. You would be surprised how many other languages "fsck up with logic". As I already mentioned MQL, you can see for yourself that || take precedence to && (which, to my feeling, hurts more than putting all in the same bowl). But well, everything has a reason. However, after people insisted (we were discussing there, same as me and you discussing here now) they changed it in version 5 of the language, to a more mathematical way.

Staying on pari, you will be even more confused when you will find out that there are no bitwise & and | operators, and in fact they are equivalent to && and respective ||, hehe.

Batalov · 2013-06-22, 08:16

Yes, but you don't see them break their own written rules, right?
Run the code with different Pari binaries, and you will see what upsets me.

Most wonderful of course is perl! "There's more than one way to do it! " (c)
Because sometimes they wanted "and" and "or" to have lowest possible precedence*, they have added "and" and "or" in addition to "&&" and "||", and all the difference is precedence. And they didn't break the rules, they just made more rules. But that's honest in my book.

_________
* obligatory example:

Code:

open IN, "<file" or die;

;-)

science_man_88 · 2013-06-22, 12:10

Quote:

Originally Posted by Batalov

Yes, but you don't see them break their own written rules, right?
Run the code with different Pari binaries, and you will see what upsets me.

Most wonderful of course is perl! "There's more than one way to do it! " (c)
Because sometimes they wanted "and" and "or" to have lowest possible precedence*, they have added "and" and "or" in addition to "&&" and "||", and all the difference is precedence. And they didn't break the rules, they just made more rules. But that's honest in my book.

_________
* obligatory example:

Code:

open IN, "<file" or die;

;-)

Code:

? n=5678027;s=0;forstep(p=n*(n-1)/2+4,n*(n+1)/2-1,[2,4],if(isprime(p),\
  if(p%6==1,a1=isprime(p+n-1);a3=isprime(p+n+1);if(a1&&(a3||isprime(p-2)||isprime(p+n+n))||(a3&&isprime(p+n+n+2)),s+=p),
  a1=isprime(p+n+1);a2=isprime(p-n+1);if(a2&&(a1||isprime(p-n*2+4))||(a1&&(isprime(p+2)||isprime(p+n+n+2))),s+=p) )));s
%5 = 79697256800321526
? n=5678027;s=0;forstep(p=n*(n-1)/2+4,n*(n+1)/2-1,[2,4],if(isprime(p),\
  if(p%6==1,a1=isprime(p+n-1);a3=isprime(p+n+1);if(a1&&(a3||isprime(p-2)||isprime(p+n+n))||(a3&&isprime(p+n+n+2)),s+=p),
  a1=isprime(p+n+1);a2=isprime(p-n+1);if((a2&&(a1||isprime(p-n*2+4)))||(a1&&(isprime(p+2)||isprime(p+n+n+2))),s+=p) )));
%6 = 79697256800321526

works in 2.5.3

CRGreathouse · 2013-06-23, 01:47

Quote:

Originally Posted by LaurV

Staying on pari, you will be even more confused when you will find out that there are no bitwise & and | operators, and in fact they are equivalent to && and respective ||, hehe.

& and | are deprecated, and have been removed in recent versions.

GP does have bitwise operators, just not convenient C-style ones: bitor, bitand, bitxor, bitnegimply.

science_man_88 · 2013-06-25, 22:36

Quote:

Originally Posted by CRGreathouse

& and | are deprecated, and have been removed in recent versions.

GP does have bitwise operators, just not convenient C-style ones: bitor, bitand, bitxor, bitnegimply.

I've been playing around with these, is there a more reliable way using them to add 2 to a number than:

Code:

 
bitneg(bitxor(bitneg(x),2))

?

CRGreathouse · 2013-06-25, 22:38

Code:

x+2

?

Maybe if you tell me what you're trying to accomplish...

science_man_88 · 2013-06-25, 22:40

Quote:

Originally Posted by CRGreathouse

Code:

x+2

?

I was thinking more with the bit operators since in some cases it seems quicker with them. I'm just simply trying to accomplish an addition of 2 just seemed to be fun instead of a forstep loop. edit:though using it for gaps between primes might be fun ( since they divide by 2)

CRGreathouse · 2013-06-25, 22:42

Quote:

Originally Posted by science_man_88

I was thinking more with the bit operators since in some cases it seems quicker with them.

Doubtful.

Code:

> for(x=1,1e6,bitneg(bitxor(bitneg(x),2)))
time = 734 ms.
> for(x=1,1e6,x+2)
time = 428 ms.

The bitwise versions need to allocate space and then copy three times instead of once, so asymptotically I expect them to take nearly three times as long.

ismillo · 2013-07-22, 00:53

Few weeks ago, I started learning PARI, then some day, I was needed to make a vector turns into an integer, I know it's possible to make an integer turn into an array using the function "digits(n)", but I need to know if somehow I can reverse it. For example: if the vector a=[1,2,3], it will turn into a=123. If the vector b=[12,3,45], it will turn into b=12345.

Thanks for anyone who can help me.

science_man_88 · 2013-07-22, 13:14

Quote:

Originally Posted by ismillo

Few weeks ago, I started learning PARI, then some day, I was needed to make a vector turns into an integer, I know it's possible to make an integer turn into an array using the function "digits(n)", but I need to know if somehow I can reverse it. For example: if the vector a=[1,2,3], it will turn into a=123. If the vector b=[12,3,45], it will turn into b=12345.

Thanks for anyone who can help me.

function names depend on version of pari and I'm no expert but:

Code:

 
a=[1,2,3];b=#a;until(#a==1,a[1]=concat(Str(a[1]),Str(a[2]));if(#a==b,a[b-1]=a[b]);a=vector(#a-1,n,a[n]));a=eval(a[1])

appears to work for me ( but is pretty complicated in my mind) ( edit:no it doesn't I made an error):

to go the same way as your digits function:

Code:

a=123;a=eval(Vec(Str(a)))

works

2013-06-22, 08:09	#2389
LaurV Romulan Interpreter Jun 2011 Thailand 9664₁₀ Posts	And that is how your world turns upside-down As a programmer-for-living for few decades, changing my tools many times (sometime few times per year, depending of the projects I was working for) I learned a good lesson: you have to know your tools. You would be surprised how many other languages "fsck up with logic". As I already mentioned MQL, you can see for yourself that \|\| take precedence to && (which, to my feeling, hurts more than putting all in the same bowl). But well, everything has a reason. However, after people insisted (we were discussing there, same as me and you discussing here now) they changed it in version 5 of the language, to a more mathematical way. Staying on pari, you will be even more confused when you will find out that there are no bitwise & and \| operators, and in fact they are equivalent to && and respective \|\|, hehe. Last fiddled with by LaurV on 2013-06-22 at 08:16

2013-06-22, 08:16	#2390
Batalov "Serge" Mar 2008 Phi(4,2^7658614+1)/2 9,497 Posts	Yes, but you don't see them break their own written rules, right? Run the code with different Pari binaries, and you will see what upsets me. Most wonderful of course is perl! "There's more than one way to do it! " (c) Because sometimes they wanted "and" and "or" to have lowest possible precedence, they have added "and" and "or" in addition to "&&" and "\|\|", and all the difference is precedence. And they didn't break the rules, they just made more rules. But that's honest in my book. _________ obligatory example: Code: open IN, "<file" or die; ;-)

2013-06-25, 22:38	#2394
CRGreathouse Aug 2006 3·1,993 Posts	Code: x+2 ? Maybe if you tell me what you're trying to accomplish... Last fiddled with by CRGreathouse on 2013-06-25 at 22:40

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2013-07-22, 00:53	#2397
ismillo Jul 2013 Brazil 19₁₀ Posts	Few weeks ago, I started learning PARI, then some day, I was needed to make a vector turns into an integer, I know it's possible to make an integer turn into an array using the function "digits(n)", but I need to know if somehow I can reverse it. For example: if the vector a=[1,2,3], it will turn into a=123. If the vector b=[12,3,45], it will turn into b=12345. Thanks for anyone who can help me.