Clarity vs. code reuse/generality

pdpi pdpinheiro at gmail.com
Tue Jul 7 20:51:59 CEST 2009


On Jul 7, 7:31 pm, pdpi <pdpinhe... at gmail.com> wrote:
> On Jul 7, 7:06 pm, Paul Rubin <http://phr...@NOSPAM.invalid> wrote:
>
> > pdpi <pdpinhe... at gmail.com> writes:
> > > Personally, I think the code is an unreadable mess, but that's mostly
> > > because of all the micro optimizations, not the generality of it.
> > > Here's my unoptimized, but still equally generic, version:
>
> > That version doesn't use "sense" inside the binary search, i.e. it
> > relies on the function being monotonically increasing.
>
> You're right, make that:
>
> def _binary_search(lo, hi, func, target, epsilon):
>     sense = cmp(func(hi), func(lo))
>     if sense == 0:
>         return None
>     guess = (lo + hi) / 2.
>     while abs(func(guess) - target) > epsilon:
>         guess = (lo + hi) / 2.
>         if sense * func(guess) > target:
>             hi = guess
>         elif sense * func(guess) < target:
>             lo = guess
>         elif lo == hi:
>             return None
>     return guess
>
> Seems I had a serious brain cramp while posting that...

Actually, scratch that.

def _binary_search(lo, hi, func, target, epsilon):
    sense = cmp(func(hi), func(lo))
    if sense == 0:
        return None
    guess = (lo + hi) / 2.
    while abs(func(guess) - target) > epsilon:
        guess = (lo + hi) / 2.
        if sense * func(guess) > sense * target:
            hi = guess
        elif sense * func(guess) < sense * target:
            lo = guess
        elif lo == hi:
            return None
    return guess



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