wow this is a bit over my range of knowledge im impressed :) ill be
happy to look at it but i think i will see if i can end up writing
my own :) worse case ill do it by hand will not take long hmm wow
thanks :)
On Sep 10, 2007, at 8:47 PM, John Fouhy wrote:
#######
import operator
binops = { 'add':operator.add,
'sub':operator.sub,
'mul':operator.mul,
'div':operator.truediv,
'pow':operator.pow,
'join':lambda x, y: int(str(x)+str(y))
}
patterns = { 'add':'(%s) + (%s)',
'sub':'(%s) - (%s)',
'mul':'(%s) * (%s)',
'div':'(%s) / (%s)',
'pow':'(%s)^(%s)',
'join':'%s%s'
}
def combine(digits):
""" digits :: set(int)
output :: [ (value, expression) ]
value :: int
expression :: str -- string representation of math expression
"""
# We're going to solve this instance in terms of the solution
# for a list with one fewer digit.
# Because of non-commutativity, we have to do this twice for each
# possible start digit.
res = []
# Base case.
if len(digits) == 1:
return [(digit, str(digit)) for digit in digits]
# Otherwise..
for digit in digits:
remainder = digits - set([digit])
for val, exp in combine(remainder):
for binop in binops:
if binop == 'join':
# Ensure we only join numbers, not expressions.
try:
int(exp)
except ValueError:
continue
try:
newval1 = binops[binop](digit, val)
pattern1 = patterns[binop] % (str(digit), exp)
res.append((newval1, pattern1))
except ZeroDivisionError:
pass
try:
newval2 = binops[binop](val, digit)
pattern2 = patterns[binop] % (exp, str(digit))
res.append((newval2, pattern2))
except ZeroDivisionError:
pass
return res
if __name__ == '__main__':
res = combine(set(range(1, 4)))
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