Hi,
i’m trying the Gecoderwithgecode library, to solve some CSP problems.
The problem is: given a int_matrix (with domain 0…1),
sched = int_var_matrix(3, 15,0..1)
place 0 and 1’s in order to respect the following constraints:

the sum of each column’s value must be 1:
sched.column_size.times do j col=sched.column(j).to_a sumc=int_var sumc=col.inject{sum,x sum+x} sumc.must==1 end

the sum of each row’s value must be equal to a given array content:
times=[3,4,3] # the array sched.row_size.times do i ro=sched.row(i).to_a sumr=int_var sumr=ro.inject{sum,y sum+y} sumr.must==times[i] end
The 1) and 2) work well, but when i put the 3rd:

each row, the first “1” from left, must be positioned after a
specific index, contained in an arraystarts=[7,3,0] # the array
sched.row_size.times do w
ro=sched.row(w).to_a
sumg=int_var
sumg=ro.index(1) {i puts i}
sumg.must >= starts
end
if i keep just the 1) and 2) and do:
branch_on matricione
solve!
i obtain a solution, but when i put the 3), it appears the following
error:
method_missing': undefined method
must’ for nil:NilClass
(NoMethodError)
from scheduling.rb:55
This is strange, because the 3) is very similar to the other ones!!
Anyone can help me please?
Thanks
Saverio