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Date: Fri, 12 Aug 2011 18:35:46 +0100
From: MRAB <python@mrabarnett.plus.com>
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Subject: Re: Java is killing me! (AKA: Java for Pythonheads?)
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On 12/08/2011 18:02, kj wrote:
>
>
>
> *Please* forgive me for asking a Java question in a Python forum.
> My only excuse for this no-no is that a Python forum is more likely
> than a Java one to have among its readers those who have had to
> deal with the same problems I'm wrestling with.
>
> Due to my job, I have to port some Python code to Java, and write
> tests for the ported code.  (Yes, I've considered finding myself
> another job, but this is not an option in the immediate future.)
>
> What's giving me the hardest time is that the original Python code
> uses a lot of functions with optional arguments (as is natural to
> do in Python).
>
> As far as I can tell (admittedly I'm no Java expert, and have not
> programmed in it since 2001), to implement a Java method with n
> optional arguments, one needs at least 2**n method definitions.
> Even if all but one of these definitions are simple wrappers that
> call the one that does all the work, it's still a lot of code to
> wade through, for nothing.
>
> That's bad enough, but even worse is writing the unit tests for
> the resulting mountain of fluffCode.  I find myself writing test
> classes whose constructors also require 2**n definitions, one for
> each form of the function to be tested...
>
> I ask myself, how does the journeyman Python programmer cope with
> such nonsense?
>
> For the sake of concreteness, consider the following run-of-the-mill
> Python function of 3 arguments (the first argument, xs, is expected
> to be either a float or a sequence of floats; the second and third
> arguments, an int and a float, are optional):
>
>     def quant(xs, nlevels=MAXN, xlim=MAXX):
>          if not hasattr(xs, '__iter__'):
>              return spam((xs,), n, xlim)[0]
>
>          if _bad_quant_args(xs, nlevels, xlim):
>              raise TypeError("invalid arguments")
>
>          retval = []
>          for x in xs:
>              # ...
>              # elaborate acrobatics that set y
>              # ...
>              retval.append(y)
>
>          return retval
>
> My Java implementation of it already requires at least 8 method
> definitions, with signatures:
>
[snip]

I would declare:

      short[] quant (float[], int    , float)
      short   quant (Float  , Integer, Float)

and see how it goes.

"float" and "int" should be boxed to "Float" and "Integer"
automatically.

If the second and third arguments are frequently the default, then I
would also declare:

      short[] quant (float[])
      short   quant (Float  )