# This is the template file for Lab #4, Task #2
import numpy
import lab4

# compute even parity for a bit sequence
def even_parity(bits):
    return sum(bits) % 2

# rect_decode -- correct errors in a rectangular block code (an SEC code)
# arguments:
#   codeword -- numpy array of bits, whose length is equal to
#                     nrows*ncols + nrows + ncols
#               (order of bits in array: all the data bits,
#               row-by-row, followed by the row parity bits,
#               followed by the column parity bits).
#   nrows -- integer, number of rows in rectangular block
#   ncols -- integer, number of columns in rectangular block
# return value:
#   numpy array of size nrows*ncols of the most likely message bits
def rect_decode(codeword,nrows,ncols):
    # Your code here
    pass

# decode_stream -- decode a stream of blocks, each block encoded with 
# a rectangular parity code.  Each block has nrows*ncols + nrows + ncols
# bits when coded.  The nrows + ncols parity bits for each block are
# immeadiately following the block.
def decode_stream(stream,nrows,ncols):
    # Your code here
    pass

if __name__ == '__main__':
    # test your implementation
    #   first tests correct decode with no errors
    #   then tests correct decode with single error
    lab4.test_rect_decode(rect_decode)
    #   then test stream decoding ability (not exhaustively)
    lab4.test_stream_decode(decode_stream)
    
    # when ready for checkoff, enable the next line.
    #lab4.checkoff(rect_decode,decode_stream,task='L4_2')