how can I insert comments into a multiline array creation?

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Andrew Diamond
Andrew Diamond 2017-12-27
评论： Fergil Mills 2019-7-15
This works
>> p = [...
%%%BEGIN ENTRIES %%%
'a1;', ...
'b;', ...
'c;'
]
p =
a1;b;c;
but commenting out the 'b' line doesn't
p = [...
%%%BEGIN ENTRIES %%%
'a1;', ...
% 'b;', ...
'c;'
]
Dimensions of matrices being concatenated are not consistent.

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采纳的回答

Walter Roberson
Walter Roberson 2017-12-27
p = [...
%%%BEGIN ENTRIES %%%
'a1;', ...
... % 'b;', ...
'c;'
]
Note: ... itself acts as a comment operator for the rest of the line, so you could get away with
p = [...
%%%BEGIN ENTRIES %%%
'a1;', ...
... 'b;', ...
'c;'
]
However this would tend to confuse people as it is not common to use this and readers might not pick up on the fact the rest of the line was a comment.
  2 个评论
Andrew Diamond
Andrew Diamond 2017-12-27
Thanks so much. So, is the idea that like a % an continuation ellipses means "ignore the rest of the line"? But then why does that work and not %? Inquiring minds want to know.
Walter Roberson
Walter Roberson 2017-12-27
... has the side effect of also ignoring the rest of the line, but it has the primary effect of continuing the previous statement.
The portion of the 'b;' line before the % is not commented out, so
p = ['a1;', ...
% 'b;', ...
'c;']
is the same as
p = ['a1;', ...
'c;']
which is not the same as
p = ['a1;', ...
'c;']
The
p = ['a1;', ...
'c;']
version should be looked at as if it were
p = ['a1;', ...
[]
'c;']
which would be the same as
p = ['a1;', []
'c;']
The default within [] is that lines that do not end in continuation are treated as if they had ; at the end of them, so this is
p = ['a1;', [];
'c;']
which is
p = ['a1;';
'c;']
and that fails because the number of columns is not equal.

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更多回答（1 个）

Andrew Diamond
Andrew Diamond 2017-12-27
I've been doing matlab for about 30 years and I didn't know this (the implicit empty array row insertion as well as the continuing ellipses at the start of a line as a continuation of the previous line etc). You learn something new every day.
again, thanks so much.

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