All interval problem in Essence'.

$CSPLib problem number 7$ http://www.csplib.org/Problems/prob007
$"""$ Given the twelve standard pitch-classes (c, c$, d, ...), represented by$ numbers 0,1,...,11, find a series in which each pitch-class occurs exactly
$once and in which the musical intervals between neighbouring notes cover$ the full set of intervals from the minor second (1 semitone) to the major
$seventh (11 semitones). That is, for each of the intervals, there is a$ pair of neigbhouring pitch-classes in the series, between which this
$interval appears. The problem of finding such a series can be easily$ formulated as an instance of a more general arithmetic problem on Z_n,
$the set of integer residues modulo n. Given n in N, find a vector$ s = (s_1, ..., s_n), such that (i) s is a permutation of
$Z_n = {0,1,...,n-1}; and (ii) the interval vector$ v = (|s_2-s_1|, |s_3-s_2|, ... |s_n-s_{n-1}|) is a permutation of
$Z_n-{0} = {1,2,...,n-1}. A vector v satisfying these conditions is$ called an all-interval series of size n; the problem of finding such
$a series is the all-interval series problem of size n. We may also be$ interested in finding all possible series of a given size.
$"""$
$Model created by Hakan Kjellerstrand, hakank@gmail.com$ See also my Essence'/Tailor page: http://www.hakank.org/savile_row/

$Licenced under CC-BY-4.0 : http://creativecommons.org/licenses/by/4.0/ language ESSENCE' 1.0 letting n be 12 letting range be domain int(1..n) letting range2 be domain int(1..n-1) find x: matrix indexed by [range] of range find diffs: matrix indexed by [range2] of range2 such that allDiff(diffs), allDiff(x), forall k : range2 . diffs[k] = |x[k+1]-x[k]|,$ symmetry breaking
x[1] < x[n-1],
diffs[1] < diffs[2]