find the lowest common denominator
01-15-2018, 10:25 AM
Post: #1
 Hamada-77 Junior Member Posts: 7 Joined: Dec 2017
find the lowest common denominator
hello
how can i find the lowest common denominator of two numbers with Hp prime ?
thanks
01-15-2018, 12:53 PM
Post: #2
 Didier Lachieze Senior Member Posts: 1,648 Joined: Dec 2013
RE: find the lowest common denominator
I'm not sure there is a build-in function providing the lowest common denominator.
So here is a small program doing that:

Code:
EXPORT LCD(N,M) BEGIN  LOCAL l:={};  l:=INTERSECT(mat2list(idivis(N)),mat2list(idivis(M)));  RETURN l(MIN(SIZE(l),2)); END;
01-15-2018, 12:59 PM
Post: #3
 Joe Horn Senior Member Posts: 2,011 Joined: Dec 2013
RE: find the lowest common denominator
(01-15-2018 12:53 PM)Didier Lachieze Wrote:  I'm not sure there is a build-in function providing the lowest common denominator.

There is: it's the lcm function (lowest common multiple). In CAS, it works on integers of any length.

lcm(12,18) --> 36
1/12+1/18 --> 5/36

It also works on polynomials, not just integers.

<0|ΙΈ|0>
-Joe-
01-15-2018, 01:20 PM (This post was last modified: 01-15-2018 01:21 PM by Didier Lachieze.)
Post: #4
 Didier Lachieze Senior Member Posts: 1,648 Joined: Dec 2013
RE: find the lowest common denominator
Good point, I misunderstood the request as beeing for the lowest common divisor.
01-16-2018, 12:31 AM
Post: #5
 john gustaf stebbins Junior Member Posts: 47 Joined: Dec 2013
RE: find the lowest common denominator
I'm getting to go through this basic math with my kids now.

I think the least common divisor can be found with the "1" function.

;^)

On the 50g, this was actually function of sort, at least a token so that this commonly used number parsed faster than a number literal. Don't know that they have done the same with the Prime.

-jgs
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