Re: How to extract the number of cols from a matrix?

If the rows of a matrix are well-constructed, each will have the same number of elements, even if some elements are undefined. my $cols = @{$mat[0]}; To check for that goodness,

@mat == grep {
    @{$_} == @{$mat[0]};
} @mat or die '@mat not well-formed';
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The equality tests put all those arrays in scalar context, so their counts are what is tested.

See tye's References quick reference for a concise key to understanding reference manipulations.

After Compline,
Zaxo

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Re^2: How to extract the number of cols from a matrix? by ikegami (Patriarch) on Jun 26, 2005 at 14:04 UTC
Instead of counting the well-formed rows when trying to determine the existence of malformed rows, I'd count the malformed ones. In effect, you're using double negation ("no not well-formed rows"), which is less clear than the straightforward approach. `die '@mat malformed' if grep { @{$_} != @{$mat[0]} } @mat;` [download]	[reply] [d/l]