A-M baby

Task/Formal-power-series/Python/formal-power-series-1.py

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+''' \
+For a discussion on pipe() and head() see
+  http://paddy3118.blogspot.com/2009/05/pipe-fitting-with-python-generators.html
+'''
+
+from itertools import islice
+from fractions import Fraction
+from functools import reduce
+try:
+    from itertools import izip as zip # for 2.6
+except:
+    pass
+
+def head(n):
+    ''' return a generator that passes through at most n items
+    '''
+    return lambda seq: islice(seq, n)
+
+def pipe(gen, *cmds):
+    ''' pipe(a,b,c,d, ...) -> yield from ...d(c(b(a)))
+    '''
+    return reduce(lambda gen, cmd: cmd(gen), cmds, gen)
+
+def sinepower():
+    n = 0
+    fac = 1
+    sign = +1
+    zero = 0
+    yield zero
+    while True:
+        n +=1
+        fac *= n
+        yield Fraction(1, fac*sign)
+        sign = -sign
+        n +=1
+        fac *= n
+        yield zero
+def cosinepower():
+    n = 0
+    fac = 1
+    sign = +1
+    yield Fraction(1,fac)
+    zero = 0
+    while True:
+        n +=1
+        fac *= n
+        yield zero
+        sign = -sign
+        n +=1
+        fac *= n
+        yield Fraction(1, fac*sign)
+def pluspower(*powergenerators):
+    for elements in zip(*powergenerators):
+        yield sum(elements)
+def minuspower(*powergenerators):
+    for elements in zip(*powergenerators):
+        yield elements[0] - sum(elements[1:])
+def mulpower(fgen,ggen):
+    'From: http://en.wikipedia.org/wiki/Power_series#Multiplication_and_division'
+    a,b = [],[]
+    for f,g in zip(fgen, ggen):
+        a.append(f)
+        b.append(g)
+        yield sum(f*g for f,g in zip(a, reversed(b)))
+def constpower(n):
+    yield n
+    while True:
+        yield 0
+def diffpower(gen):
+    'differentiatiate power series'
+    next(gen)
+    for n, an in enumerate(gen, start=1):
+        yield an*n
+def intgpower(k=0):
+    'integrate power series with constant k'
+    def _intgpower(gen):
+        yield k
+        for n, an in enumerate(gen, start=1):
+            yield an * Fraction(1,n)
+    return _intgpower
+
+
+print("cosine")
+c = list(pipe(cosinepower(), head(10)))
+print(c)
+print("sine")
+s = list(pipe(sinepower(), head(10)))
+print(s)
+# integrate cosine
+integc = list(pipe(cosinepower(),intgpower(0), head(10)))
+# 1 - (integrate sine)
+integs1 = list(minuspower(pipe(constpower(1), head(10)),
+                          pipe(sinepower(),intgpower(0), head(10))))
+
+assert s == integc, "The integral of cos should be sin"
+assert c == integs1, "1 minus the integral of sin should be cos"

Task/Formal-power-series/Python/formal-power-series-2.py

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+from itertools import islice, tee
+from fractions import Fraction
+try:
+    from itertools import izip as zip # for 2.6
+except:
+    pass
+
+def pluspower(*powergenerators):
+    for elements in zip(*powergenerators):
+        yield sum(elements)
+def minuspower(*powergenerators):
+    for elements in zip(*powergenerators):
+        yield elements[0] - sum(elements[1:])
+def mulpower(fgen,ggen):
+    'From: http://en.wikipedia.org/wiki/Power_series#Multiplication_and_division'
+    a,b = [],[]
+    for f,g in zip(fgen, ggen):
+        a.append(f)
+        b.append(g)
+        yield sum(f*g for f,g in zip(a, reversed(b)))
+def constpower(n):
+    yield n
+    while True:
+        yield 0
+def diffpower(gen):
+    'differentiatiate power series'
+    next(gen)
+    for n, an in enumerate(gen, start=1):
+        yield an*n
+def intgpower(gen):
+    'integrate power series with bounds from 0 to x'
+    yield 0
+    for n, an in enumerate(gen, start=1):
+        yield an * Fraction(1,n)
+
+
+def sine_cosine_series():
+    def deferred_sin():
+        for i in sinx_temp:
+            yield i
+    def deferred_cos():
+        for i in cosx_temp:
+            yield i
+
+    sinx_result, sinx_copy1 = tee(deferred_sin(), 2)
+    cosx_result, cosx_copy1 = tee(deferred_cos(), 2)
+
+    sinx_temp = intgpower(cosx_copy1)
+    cosx_temp = minuspower(constpower(1), intgpower(sinx_copy1))
+
+    return sinx_result, cosx_result
+
+sinx, cosx = sine_cosine_series()
+
+print("cosine")
+print(list(islice(sinx, 10)))
+print("sine")
+print(list(islice(cosx, 10)))