show_with_coalesced_runs.py

"""
Problem from David Albert
'bumps' idea from Michael Arntzenius & Eugene Ha
"""

def repr_register_bits(bits):
    return '/'.join(repr_bits('D', bits & 0xFF) + repr_bits('A', bits >> 8))

def repr_bits(label, bits):
    bits = [(bits>>i) & 1 for i in range(8)]
    bumps = [next_b - b for b,next_b in zip([0]+bits, bits+[0])]
    return [repr_range(label, r) for r in zip(where(1, bumps), where(-1, bumps))]

def repr_range(label, (start, after)):
    i, j = start, after-1
    return '%s%d' % (label, i) if i==j else '%s%d-%s%d' % (label, i, label, j)
    
def where(target, things):
    return [i for i,thing in enumerate(things) if thing == target]

## repr_register_bits(0x1221)
#. 'D0/D5/A1/A4'
## repr_register_bits(0xfc2f)
#. 'D0-D3/D5/A2-A7'