Cythonize trampoline

[suned]

Trampoline is used extensively to build stack safe, recursive structures, e.g in reader and state. When interpreting these structures, a significant amount of time is spent in the main loop of Trampoline.run. Consider this:

In [13]: from pfun.reader import value, sequence

In [14]: r = sequence([value(v) for v in range(100000)])

In [15]: %prun r.run(None)
         9799985 function calls in 18.876 seconds

   Ordered by: internal time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
   100000    7.918    0.000    8.201    0.000 monad.py:31(<lambda>)
        1    5.780    5.780   19.344   19.344 trampoline.py:51(run)
  1599995    1.396    0.000    1.616    0.000 typing.py:806(__new__)
   599996    0.557    0.000    1.350    0.000 trampoline.py:32(and_then)
   200000    0.406    0.000    1.588    0.000 reader.py:45(<lambda>)
   799994    0.402    0.000    0.402    0.000 <string>:1(__init__)
   399996    0.261    0.000   11.689    0.000 trampoline.py:85(_handle_cont)
   600001    0.226    0.000    0.472    0.000 {built-in method builtins.isinstance}
   599996    0.221    0.000   12.953    0.000 trampoline.py:105(_resume)
  1599995    0.220    0.000    0.220    0.000 {built-in method __new__ of type object at 0x107597830}
   199998    0.184    0.000    0.462    0.000 trampoline.py:108(and_then)
   200000    0.180    0.000    0.459    0.000 reader.py:46(<lambda>)
   200000    0.151    0.000    0.588    0.000 reader.py:44(<lambda>)
   200001    0.143    0.000    0.376    0.000 reader.py:95(<lambda>)
   600001    0.139    0.000    0.611    0.000 trampoline.py:28(_is_done)
   199998    0.134    0.000    0.975    0.000 trampoline.py:113(<lambda>)
   600000    0.128    0.000    0.128    0.000 {built-in method _abc._abc_instancecheck}
   600000    0.119    0.000    0.246    0.000 abc.py:137(__instancecheck__)
   100000    0.108    0.000    0.283    0.000 reader.py:84(value)
   100000    0.079    0.000    0.204    0.000 reader.py:26(and_then)
   200000    0.068    0.000    1.043    0.000 trampoline.py:74(_handle_cont)
   100000    0.058    0.000    0.262    0.000 monad.py:30(<lambda>)
        1    0.000    0.000   19.344   19.344 <string>:1(<module>)
        3    0.000    0.000    0.000    0.000 future.py:47(__del__)
        1    0.000    0.000   19.344   19.344 {built-in method builtins.exec}
        1    0.000    0.000   19.344   19.344 reader.py:67(run)
        1    0.000    0.000    0.000    0.000 typing.py:245(inner)
        1    0.000    0.000    0.000    0.000 typing.py:890(cast)
        4    0.000    0.000    0.000    0.000 trampoline.py:89(_resume)
        1    0.000    0.000    0.000    0.000 {method 'disable' of '_lsprof.Profiler' objects}

Most of the execution time is spent in Trampoline.run. Optimising this loop is therefore a reasonable investment since it will speed up every usage of trampolines.