Talk:Vigenère cipher/Cryptanalysis: Difference between revisions

::::: It looks like the editor changed instances of 'out' to 'result' to avoid sharing symbol names with VigenereAnalyser::out. That's a reasonable change for defensive coding. I don't see the value of changing it from 'class' to 'struct'...the only consequence I know of is that 'struct' has all members default to 'public', instead of 'private', and I don't see a need for any of the class's members to be public except the constructor and analyze(). There were a lot of changes from using 'int' to using 'size_t' in loops. That's generally sensible for any time one is calling into array indexes; size_t will tend to be the systems largest unsigned integer type. He split one common across two lines, so I presume he was cleaning code up for 80-char-wide presentation. That's a common style preference. He removed VigenereAnalyser::key as a member variable, and made it a function-scope stack variable, which is reasonable enough; it helps make it clear that the variable is only for use in that function, and I suppose the allocation cost for a function called once in the class's lifetime is not a significant concern. (It looks like he generally reduced the scope lifetimes of the variables used in analyze(). See corr, for example; it was moved to being declared inside the code block it was used in. That's o...k, as long as the variables are simple and their allocation/deallocation expense isn't going to be spent comparatively often. If it were a more complicated type, I'd have kept it outside that for(..) loop. It comes down to the individual coder's perception of the performance tradeoff vs code readability.) Replacing '> >' with '>>' was unnecessary, but probably intended as part of showcasing differences between C++0x and C++03. gcc throws warnings on the form, though Microsoft's compiler hasn't complained at me for using '>>' as far back as VS2005. I'd venture a guess he was actively cleaning up the code in preparation for some kind of presentation. --[[User:Short Circuit|Michael Mol]] 20:42, 22 June 2011 (UTC)

::::: I went to do some changes of my own yesterday, but was stymied by my not having a C++0x compiler handy enough to stick with it; codepad.org hasn't upgraded yet. I'd make the further change of using std::vector for frequency()'s buffer, but making it a class member variable. I'd have frequency() take a reference as an argument, and pass a reference as its return value. And there were some other dependent changes, but that completely avoids the reallocation issue; frequency()'s buffer gets re-written from scratch each call through, so there's no need to clear and reinitialize separately. Just pass double(26) into its constructor as part of the class's constructor. --[[User:Short Circuit|Michael Mol]] 20:42, 22 June 2011 (UTC)

:::: Actually, using the C++0x array class might be appropriate here. It's size is a compile-time constant, but it can still be sorted and everything. (Actually, I'm not sure, but I think you can sort a normal array too, but the array class is safer.) [[User:MagiMaster|MagiMaster]] 19:52, 21 June 2011 (UTC)