[Tutor] A better way for greatest common divisor
steve at pearwood.info
Sat Jul 31 05:51:55 CEST 2010
On Sat, 31 Jul 2010 01:03:27 pm David Hutto wrote:
> This fixes the floating point 'bug' when numerator is greater than
> denominator: http://python.pastebin.com/bJ5UzsBE
I don't mean to be disparaging ... ah hell, who am I fooling? Yes I do.
What is that mess? *wink*
I can see at least four problems with that:
1. You have a function called "gcd" that doesn't calculate the gcd, but
does something else as well. That makes it a misleading name.
2. The principles of code reuse and encapsulation suggest that each
function should (as much as possible) do one thing, and do it well. You
have a function that tries to do two or three things. You should have a
single function to calculate the gcd, and a second function to use the
gcd for reducing a fraction as needed, and potentially a third function
to report the results to the user.
3. Your function has a serious bug. To see it, call gcd(5, 5) and see
what it doesn't do.
4. Code duplication. Your function repeats fairly major chunks of code.
Copy-and-paste programming is one of the Deadly Sins for programmers.
The way to get rid of that is by encapsulating code in functions (see
point 1 above).
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