ANN: Dogelog Runtime, Prolog to the Moon (2021)
Mostowski Collapse
bursejan at gmail.com
Wed Sep 15 14:48:18 EDT 2021
And how do you iterate over the first n-1 elements
of a list with n elements? This is what my code does:
i = 0
while i < len(term.args) - 1:
____mark_term(term.args[i])
____i += 1
term = term.args[i]
You can try yourself:
% python3
>>> foo = ["a", "b", "c"]
>>> i = 0
>>> while i < len(foo) - 1:
... print("mark_term", foo[i])
... i += 1
...
mark_term a
mark_term b
>>> foo = foo[i]
>>> foo
'c'
alister schrieb am Mittwoch, 15. September 2021 um 20:41:12 UTC+2:
> On Wed, 15 Sep 2021 11:31:48 -0700, Mostowski Collapse wrote:
>
> > There is a further problem with this:
> >
> >> for i,term in enumerate(term.args):
> >> ____mark_term(term.args[i])
> >
> > It should read:
> >
> > for i,help in enumerate(term.args):
> > ____mark_term(help)
> >
> > But then i isn't need.
> even Better (i had only skimmed the code as I was certain I would find
> this, it is probably the No. 1 thing new python programmers get wrong
> if your example is correct the it can be simplified even further to
>
> for help in term.args:
> mark_term(help)
>
> & if help does not get used after this loop then a comprehension is even
> better
> _ == [mark_term(help) for help in term.args]
>
>
> the underscore character is python convention for an unneeded place-
> holder variable.
> >
> > Mostowski Collapse schrieb am Mittwoch, 15. September 2021 um 20:22:50
> > UTC+2:
> >> Do you mean, replace this:
> >> i = 0 while i < len(term.args) - 1:
> >> ____mark_term(term.args[i])
> >> ____i += 1 term = term.args[i]
> >>
> >> By this:
> >>
> >> for i,term in enumerate(term.args):
> >> ____mark_term(term.args[i])
> >>
> >> This wouldn't be correct anymore. The recursive call is only for the
> >> arguments except for the last one one.
> >> alister schrieb am Mittwoch, 15. September 2021 um 20:17:23 UTC+2:
> >> > On Wed, 15 Sep 2021 18:23:10 +0200, Mostowski Collapse wrote:
> >> >
> >> > > I really wonder why my Python implementation is a factor 40 slower
> >> > > than my JavaScript implementation.
> >> > > Structurally its the same code.
> >> > >
> >> > > You can check yourself:
> >> > >
> >> > > Python Version:
> >> > > https://github.com/jburse/dogelog-moon/blob/main/devel/runtimepy/
> >> > machine.py
> >> > >
> >> > > JavaScript Version:
> >> > > https://github.com/jburse/dogelog-moon/blob/main/devel/runtime/
> >> > machine.js
> >> > >
> >> > > Its the same while, if-then-else, etc.. its the same classes
> >> > > Variable, Compound etc.. Maybe I could speed it up by some details.
> >> > > For example to create an array of length n, I use in Python:
> >> > >
> >> > > temp = [NotImplemented] * code[pos]
> >> > > pos += 1
> >> > >
> >> > > Whereas in JavaScript I use, also in exec_build2():
> >> > >
> >> > > temp = new Array(code[pos++]);
> >> > >
> >> > > So I hear Guido doesn't like ++. So in Python I use +=
> >> > > and a separate statement as a workaround. But otherwise,
> >> > > what about the creation of an array,
> >> > >
> >> > > is the the idiom [_] * _ slow? I am assuming its compiled away. Or
> >> > > does it really first create an array of size 1 and then enlarge it?
> >> > >
> >> > > Julio Di Egidio wrote:
> >> > <sniped due to top posting>
> >> >
> >> > this is probably a string contender
> >> >
> >> > i = 0 while i < len(term.args) - 1:
> >> > mark_term(term.args[i])
> >> > i += 1 term = term.args[i]
> >> >
> >> > try replacing with something more pythonic
> >> >
> >> > for index,term in enumerate(term.args):
> >> > mark_term(term.args[i])
> >> >
> >> >
> >> > & possibly go all the way to changing it into a comprehension
> >> >
> >> > there are other similar anti patterns throughout this code.
> >> >
> >> > any time you are manually keeping a counter as an index into a
> >> > list,tupple other iterable YOU ARE DOING IT WRONG!
> >> >
> >> > Do not write javascript in python, write python
> >> >
> >> >
> >> >
> >> > --
> >> > Two percent of zero is almost nothing.
> >> >
> >> >
> >> >
> >> >
> >> > --
> >> > Whoever dies with the most toys wins.
> --
> Pie are not square. Pie are round. Cornbread are square.
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