def read_mat(file, target_chr = None):
"""Generator: for returning the contents of a mat file (e.g. hg18_genes.mat) on a given chromosome."""
wp = open(file)
for line in wp:
A = re.split("\s+", line.rstrip())
if (target_chr and A[1] != target_chr):
continue
partNo = int(A[0])
start = int(A[2])
finish = int(A[3])
family = A[5]
M = sparse2matrix(" ".join(A[8:]))
R = RptMatrix(None, None)
R.class_name = A[5]
R.rep_name = A[6]
R.M = reduce_64matrix(M)
yield partNo, start, finish, R
