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## bug#6869: Octave mode: incorrect "unbalanced block" warning

**From**: |
Sprague, Webb (OFM) |

**Subject**: |
bug#6869: Octave mode: incorrect "unbalanced block" warning |

**Date**: |
Tue, 17 Aug 2010 08:34:35 -0700 |

Hi Stefan. See below...
>* It's a bug in octave's indentation code, indeed. It gets confused by*
>* the "end" in the following line:*
>* *
>* > x = data(:,2:end);*
Oh -- that makes sense.
>* *
>* I don't know Octave much, as it so happens but I've recently been*
>* playing with a new indentation code for Octave (using SMIE), so I'm*
>* interested in fixing it. Could you explain to me what is this "end"*
>* (and more generally what the "data(:,2:end)" means: all I can guess is*
>* that it's an array indexing of some sort).*
There are two uses for "end" that are pretty different:
1. Closing blocks (e.g. "if x==1 y=3 end")
2. Indexing arrays. Here "end" is evaluated to give the length of a
dimension in the array. For example if x=[2 3 4 5], then x(end) == 5,
x(end-1) == 4, etc.
Note that ":" means all elements when evaluated as an index, and "x:y"
gives the vector of elements between x and y, and "3:end" means [3 4 5
... end] where end is the max index. So, "data(:,2:end)" means all the
rows of data (the first ":") and the columns from 2 to the end.
Does that make sense?
If you really want to learn octave and don't have much experience with
matlab I would suggest Attaway's book on matlab. Octave tracks it
pretty closely.
Thanks so much for dealing with this! I sort of have my hands full, and
emacs indentation code just freaks me out ;)