PARI's commands - Page 165

science_man_88 · 2010-11-29, 21:17

Code:

longmultiply(a,b)= c=eval(Vec(Str(a)));d=eval(Vec(Str(b)));carry=0;answer=vector(length(d)+length(c));forstep(x=#d,1,[-1],forstepn=((c[y]*d[x])+carry)%10;answer[#answer-((#d-x+1)+(#c-y+1)-1)]=(answer[#answer-((#d-x+1)+(#c-y+1)-1)]+n);carry=floor((c[y]*d[x])/10)));forstep(w=#answer,1,-1,if(w>1,answer[w-1]=answer[w-1]+floor(answer[w]/10));answer[w]=answer[w]%10;if(w<#answer,answer[w+1]=answer[w]))

There we are lol, only 398 characters long! Anyone want to better this ? sorry even more for a good copy apparently lol, well I've lost a part I'll be back.

science_man_88 · 2010-11-29, 22:04

Code:

longmultiply(a,b)= c=eval(Vec(Str(a)));d=eval(Vec(Str(b)));carry=0;answer=vector(length(d)+length(c));forstep(x=#d,1,[-1],forstep(y=#c,1,[-1],n=((c[y]*d[x])+carry)%10;answer[#answer-((#d-x+1)+(#c-y+1)-1)]=(answer[#answer-((#d-x+1)+(#c-y+1)-1)]+n);carry=floor((c[y]*d[x])/10)));forstep(w=#answer,1,-1,if(w>1,answer[w-1]=answer[w-1]+floor(answer[w]/10));answer[w]=answer[w]%10;if(w<#answer,answer[w+1]=answer[w]))

Found my best answer in Pari still only works if the answer is n+m digits. 399 characters. not sure how to compensate for the last part credit should go to CRG in fact I have to give him credit for the others as well I'll correct that.

science_man_88 · 2010-11-29, 22:37

add

Code:

;answer[2]=answer[1]%10;answer[1]=floor(answer[1]/10);answer

onto it I think it then works.

science_man_88 · 2010-11-29, 22:39

Quote:

Originally Posted by science_man_88

add

Code:

;answer[2]=answer[1]%10;answer[1]=floor(answer[1]/10);answer

onto it I think it then works.

Code:

longmultiply(a,b)= c=eval(Vec(Str(a)));d=eval(Vec(Str(b)));carry=0;answer=vector(length(d)+length(c));forstep(x=#d,1,[-1],forstep(y=#c,1,[-1],n=((c[y]*d[x])+carry)%10;answer[#answer-((#d-x+1)+(#c-y+1)-1)]=(answer[#answer-((#d-x+1)+(#c-y+1)-1)]+n);carry=floor((c[y]*d[x])/10)));forstep(w=#answer,1,-1,if(w>1,answer[w-1]=answer[w-1]+floor(answer[w]/10));answer[w]=answer[w]%10;if(w<#answer,answer[w+1]=answer[w]));answer[2]=answer[1]%10;answer[1]=floor(answer[1]/10);answer

I believe. Now it's 471 characters, That's a long code in my books lol.

found a flaw in my add on.

without the addon lower ones work with it low ones don't. But for higher ones it messes it up the other way round I think.

4now I've got 33*33 not working man I suck at this.

science_man_88 · 2010-11-29, 23:19

Code:

longmultiply(a,b)= c=eval(Vec(Str(a)));d=eval(Vec(Str(b)));carry=0;answer=vector(length(d)+length(c));forstep(x=#d,1,[-1],forstep(y=#c,1,[-1],n=((c[y]*d[x])+carry)%10;answer[#answer-((#d-x+1)+(#c-y+1)-1)]=(answer[#answer-((#d-x+1)+(#c-y+1)-1)]+n);carry=floor((c[y]*d[x])/10)));forstep(w=#answer,2,-1,answer[w-1]=answer[w-1]+floor(answer[w]/10);answer[w]=answer[w]%10;if(w<#answer,answer[w+1]=answer[w]));answer[2]=answer[1]%10;answer[1]=floor(answer[1]/10);answer

I'm quiting this for now if this isn't it lol. It took me multiple post on here and 255 + answers in Pari.

science_man_88 · 2010-11-29, 23:41

Code:

***   bug in PARI/GP (Segmentation Fault), please report

not good I may close Pari lol just to restart.

science_man_88 · 2010-11-30, 00:08

Quote:

Originally Posted by science_man_88

Code:

longmultiply(a,b)= c=eval(Vec(Str(a)));d=eval(Vec(Str(b)));carry=0;answer=vector(length(d)+length(c));forstep(x=#d,1,[-1],forstep(y=#c,1,[-1],n=((c[y]*d[x])+carry)%10;answer[#answer-((#d-x+1)+(#c-y+1)-1)]=(answer[#answer-((#d-x+1)+(#c-y+1)-1)]+n);carry=floor((c[y]*d[x])/10)));forstep(w=#answer,2,-1,answer[w-1]=answer[w-1]+floor(answer[w]/10);answer[w]=answer[w]%10;if(w<#answer,answer[w+1]=answer[w]));answer[2]=answer[1]%10;answer[1]=floor(answer[1]/10);answer

I'm quiting this for now if this isn't it lol. It took me multiple post on here and 255 + answers in Pari.

and adding:

Code:

if(answer==eval(Vec(Str(a*b))),print(answer))

I get:

Code:

[1, 0, 0, 1]
[1, 0, 1, 2]
[1, 0, 2, 3]
[1, 0, 3, 4]
[1, 0, 4, 5]
[1, 0, 5, 6]
[1, 0, 6, 7]
[1, 0, 7, 8]
[1, 0, 8, 9]
[1, 0, 0, 8]
[1, 0, 2, 0]
[1, 0, 3, 2]
[1, 0, 4, 4]
[1, 0, 5, 6]
[1, 0, 0, 1]
[1, 0, 0, 8]
[1, 0, 2, 2]
[1, 0, 3, 6]
[1, 0, 5, 0]
[1, 0, 6, 4]
[1, 0, 7, 8]
[1, 0, 0, 8]
[1, 0, 2, 4]
[1, 0, 4, 0]
[1, 0, 5, 6]
[1, 0, 0, 7]
[1, 0, 2, 6]
[1, 0, 4, 5]
[1, 0, 1, 2]
[1, 0, 0, 8]
[1, 0, 3, 2]
[1, 0, 5, 6]
[1, 0, 2, 3]
[1, 0, 2, 4]
[1, 0, 5, 6]
[1, 0, 2, 3]
[1, 0, 5, 6]
[1, 0, 8, 9]
[1, 0, 1, 2]
[1, 0, 3, 4]
[1, 0, 0, 8]
[1, 0, 5, 6]
[1, 0, 2, 9]
[1, 0, 7, 8]
[1, 0, 0, 1]
[1, 0, 1, 2]
[1, 0, 2, 3]
[1, 0, 3, 4]
[1, 0, 4, 5]
[1, 0, 5, 6]
[1, 0, 6, 7]
[1, 0, 7, 8]
[1, 0, 8, 9]

far from what is expected for:

Code:

for(x=1,100,for(y=1,100,longmultiply(x,y)))

CRGreathouse · 2010-11-30, 01:22

First of all, your code seems to be nearly there -- it works in many cases. Some of the cases where it doesn't work are as simple as having an initial 0 -- in those cases you can just replace the final

Code:

;answer

with

Code:

;if(answer[1],answer,vecextract(answer,2^#answer-2))

to drop the zero. (I suppose you should also test to see if one number is 0 since in that case you'll only need one digit.)

I'm not sure what the problem is in the other case; I've avoided looking at your code since it's not formatted. But keep looking at the cases that it fails at -- why those and not others? What's going wrong there?

science_man_88 · 2010-11-30, 01:27

Quote:

Originally Posted by CRGreathouse

First of all, your code seems to be nearly there -- it works in many cases. Some of the cases where it doesn't work are as simple as having an initial 0 -- in those cases you can just replace the final

Code:

;answer

with

Code:

;if(answer[1],answer,vecextract(answer,2^#answer-2))

to drop the zero. (I suppose you should also test to see if one number is 0 since in that case you'll only need one digit.)

I'm not sure what the problem is in the other case; I've avoided looking at your code since it's not formatted. But keep looking at the cases that it fails at -- why those and not others? What's going wrong there?

Code:

longmultiply(a,b)= {
c=eval(Vec(Str(a)));
d=eval(Vec(Str(b)));
carry=0;
answer=vector(length(d)+length(c));
forstep(x=#d,1,[-1],
forstep(y=#c,1,[-1],
n=((c[y]*d[x])+carry)%10;
answer[#answer-((#d-x+1)+(#c-y+1)-1)]=(answer[#answer-((#d-x+1)+(#c-y+1)-1)]+n);
carry=floor((c[y]*d[x])/10)));
forstep(w=#answer,2,-1,
answer[w-1]=answer[w-1]+floor(answer[w]/10);
answer[w]=answer[w]%10;
if(w<#answer,answer[w+1]=answer[w]));
answer[2]=answer[1]%10;
answer[1]=floor(answer[1]/10);
answer
}

is this formatted better ?

CRGreathouse · 2010-11-30, 01:43

Quote:

Originally Posted by science_man_88

is this formatted better ?

A little. Here's how I'd format it:

Code:

longmultiply(a,b)= {
	my(c=eval(Vec(Str(a))),d=eval(Vec(Str(b))),carry=0,answer=vector(#c+#d));
	forstep(x=#d,1,[-1],
		forstep(y=#c,1,[-1],
			n=((c[y]*d[x])+carry)%10;
			answer[#answer-((#d-x+1)+(#c-y+1)-1)] += n;
			carry=(c[y]*d[x])\10
		)
	);
	forstep(w=#answer,2,-1,
		answer[w-1] += answer[w]\10;
		answer[w]=answer[w]%10;
		if(w<#answer,answer[w+1]=answer[w])
	);
	answer[2]=answer[1]%10;
	answer[1]=answer[1]\10;
	answer
};

Also changed: length(foo) to #foo, floor(foo/10) to foo\10, foo = foo + n to foo += n, local variables put into a my block. (This is important if you want to avoid clobbering variables! Always do this!)

science_man_88 · 2010-11-30, 01:49

Quote:

Originally Posted by CRGreathouse

A little. Here's how I'd format it:

Code:

longmultiply(a,b)= {
	my(c=eval(Vec(Str(a))),d=eval(Vec(Str(b))),carry=0,answer=vector(#c+#d));
	forstep(x=#d,1,[-1],
		forstep(y=#c,1,[-1],
			n=((c[y]*d[x])+carry)%10;
			answer[#answer-((#d-x+1)+(#c-y+1)-1)] += n;
			carry=(c[y]*d[x])\10
		)
	);
	forstep(w=#answer,2,-1,
		answer[w-1] += answer[w]\10;
		answer[w]=answer[w]%10;
		if(w<#answer,answer[w+1]=answer[w])
	);
	answer[2]=answer[1]%10;
	answer[1]=answer[1]\10;
	answer
};

Also changed: length(foo) to #foo, floor(foo/10) to foo\10, foo = foo + n to foo += n, local variables put into a my block. (This is important if you want to avoid clobbering variables! Always do this!)

the red is the starts with 0 error, I should add an if around it checking if answer[1]>10 first if so i doubt after the previous step that answer[1] is useful.

2010-11-29, 22:37	#1807
science_man_88 "Forget I exist" Jul 2009 Dumbassville 2⁶×131 Posts	add Code: ;answer[2]=answer[1]%10;answer[1]=floor(answer[1]/10);answer onto it I think it then works.

2010-11-29, 23:41	#1810
science_man_88 "Forget I exist" Jul 2009 Dumbassville 8384₁₀ Posts	Code: *** bug in PARI/GP (Segmentation Fault), please report not good I may close Pari lol just to restart.

2010-11-30, 01:22	#1812
CRGreathouse Aug 2006 3×1,993 Posts	First of all, your code seems to be nearly there -- it works in many cases. Some of the cases where it doesn't work are as simple as having an initial 0 -- in those cases you can just replace the final Code: ;answer with Code: ;if(answer[1],answer,vecextract(answer,2^#answer-2)) to drop the zero. (I suppose you should also test to see if one number is 0 since in that case you'll only need one digit.) I'm not sure what the problem is in the other case; I've avoided looking at your code since it's not formatted. But keep looking at the cases that it fails at -- why those and not others? What's going wrong there?

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