[Tutor] comparing seqs by successive intervals

[kevin parks]

Don asks:

> Forgive my asking, but what would this sort of comparison be used for? 
> The
> problem seems strange enough to make it sound an awful lot like a 
> homework
> assignment.

It would be used for comparing musical sequences to see if they are 
related by transposition or inversion (get to that later). Two musical 
sequences that have different pitches are related by transposition if 
their interval sequences are the same. I would be using this to test 
for that condition.

It is not a homework assignment. It is just something i am trying to 
hack together for my own personal
library of python modules. Mostly cause i am insane and do this on a 
sat night for fun.

Lee suggests:


> How about "normalizing" each list?
>
>>>> seq01 = [5, 7, 8, 11]
>>>> s01 = [s - seq01[0] for s in seq01]
>>>> s01
> [0, 2, 3, 6]
>>>> seq02 = [1, 3, 4, 7]
>>>> s02 = [s - seq02[0] for s in seq02]
>>>> s02
> [0, 2, 3, 6]
>

Actually I am doing something similar to this in some other code. I 
have something that removes duplicates and sorts the items beforehand, 
then normalizes as above. And of course normalizing will show that 
there are indeed transpositions (i have code that does this too) but i 
was intrigued and puzzled by this idea of measuring the intervals 
between successive list items and wanted to see how that could be done 
and then compared to another list, because i eventually find a way to 
see how far away the transposed items are.... eventually.

I see that Don has sent something like is close to what i am trying to 
do, only his seems to work *^-^*, I am going to look at that now.

Thanks for the responses.


-kevin