Re: Lagrange Polynomials in Perl

You cannot shift an array off the argument stack: my @x = shift;

Assuming you are calling this as: lagrange( \@vals, \@funcs );

What you are shifting of the argument stack is an array reference; and to do that properly you need to assign it to a scalar variable:

    my $refX = shift;
[download]

And then indirect through that to get your values:

          $den *= ( $refX->[$i] - $refX->[$j] );
[download]

Do that for both your parameter arrays -- athough you do not seem to ever use @f anywhere in that function?

Also, what do you think this does: my $point = @x;?

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Re^2: Lagrange Polynomials in Perl by Mascasc (Novice) on Apr 28, 2015 at 19:56 UTC
Does $scalar = @array produce a scalar containing the size of the array?	[reply]
Re^3: Lagrange Polynomials in Perl by BrowserUk (Patriarch) on Apr 28, 2015 at 20:42 UTC
Does $scalar = @array produce a scalar containing the size of the array? Yes. But `$point` is a strange name for the size of an array! If that is meant to be short for `$lastPoint`, it is still deceptive as with zero-based arrays, the index of the last point in the array is one less than the size of the array. (Which incidentally, can be obtained using `my $lastPoint = $#array;`) With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". I'm with torvalds on this In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked	[reply] [d/l] [select]
Re^4: Lagrange Polynomials in Perl by Mascasc (Novice) on Apr 29, 2015 at 14:36 UTC
Yeah, I was thinking of it as the stopping point for the for loop more than the last point, although you are right...it's pretty unclear.	[reply]
Re^5: Lagrange Polynomials in Perl by BrowserUk (Patriarch) on Apr 29, 2015 at 15:08 UTC
Re^6: Lagrange Polynomials in Perl by Mascasc (Novice) on Apr 29, 2015 at 15:42 UTC
Re^3: Lagrange Polynomials in Perl by Laurent_R (Canon) on Apr 28, 2015 at 20:25 UTC
Yes, it does, but I would rather write: `my $array_count = scalar @array;` [download] or, omitting the scalar built-in unnecessary in scalar context: `my $array_count = @array;` [download] But I often prefer to add the `scalar` built-in, even when not necessary, just to make my intent clearer to the maintainer (which, incidentally, one year from now, might be me, and such indication might prove useful to help me understand the intent of the code). Update: removed the scalar* word which I had forgotten to omit in the second snippet. Thanks to Athanasius for pointing it out.* Je suis Charlie.	[reply] [d/l] [select]


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