/usr/share/pyshared/sympy/utilities/memoization.py is in python-sympy 0.7.1.rc1-2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | def recurrence_memo(initial):
"""
Memo decorator for sequences defined by recurrence
See usage examples e.g. in the specfun/combinatorial module
"""
cache = initial
def decorator(f):
def g(n):
L = len(cache)
if n <= L - 1:
return cache[n]
for i in xrange(L, n+1):
cache.append(f(i, cache))
return cache[-1]
return g
return decorator
def assoc_recurrence_memo(base_seq):
"""
Memo decorator for associated sequences defined by recurrence starting from base
base_seq(n) -- callable to get base sequence elements
XXX works only for Pn0 = base_seq(0) cases
XXX works only for m <= n cases
"""
cache = []
def decorator(f):
def g(n,m):
L = len(cache)
if n < L:
return cache[n][m]
for i in xrange(L,n+1):
# get base sequence
F_i0 = base_seq(i)
F_i_cache = [F_i0]
cache.append(F_i_cache)
# XXX only works for m <= n cases
# generate assoc sequence
for j in xrange(1,i+1):
F_ij = f(i,j, cache)
F_i_cache.append(F_ij)
return cache[n][m]
return g
return decorator
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