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https://github.com/zekexiao/pocketlang.git
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82 lines
1.6 KiB
Plaintext
82 lines
1.6 KiB
Plaintext
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## Tail call optimization implementation.
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from lang import clock
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## Reference:
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## !!CON2019. TAIL CALL OPTIMIZATION (The musical)
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## https://www.youtube.com/watch?v=-PX0BV9hGZY
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N = 10000
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def woo(n)
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if n == 0 then return '' end
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return woo(n-1) + '!'
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end
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def woo_toc(n, acc)
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if n == 0 then return acc end
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return woo_toc(n-1, acc + '!')
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end
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s = clock()
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print(woo_toc(N, ''))
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print('elapsed:', clock() - s)
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## ----------------------------------------------------------------------------
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def fac_toc(n, acc)
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if n == 0 then return acc end
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return fac_toc(n-1, acc*n)
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end
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def fac(n)
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if n == 0 then return 1 end
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return fac(n-1) * n
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end
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## Limiting to 50 because fac(i) will
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## cause a stack overflow
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for i in 0..50
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fi = fac(i);
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ft = fac_toc(i, 1)
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if i < 24
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assert(fi == ft)
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else ## For huge values it'll differ by a tiny value.
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assert((fi - ft)/ft < 0.00000000001)
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end
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end
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## This will run without any problem but we can't
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## assert the return value since it's WAY too large for
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## a 64 bit value (100000! = 2.824229407 E+456573).
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start = clock()
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fac_toc(100000, 1)
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## expected 0.006s average (on my pc, spec on readme).
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print('fac_toc(100000, 1): elapsed:', clock() - start, 's')
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assert(true)
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def g(n)
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if n == 0 then return 1 end
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return f(n -1)
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end
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def f(n)
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if n == 0 then return 0 end
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return g(n-1)
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end
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for i in 0..100
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assert(i%2 == f(i))
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end
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## The below function caused a bug after compile time stack size calculation
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## bug fixed. Added here to check for regression.
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def h()
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f() ## <-- Not tail called here (anymore) because it's not returned.
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end
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# If we got here, that means all test were passed.
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print('All TESTS PASSED')
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