Linked by MOS6510 on Thu 10th Jan 2013 23:25 UTC
General Development "For years I've tried my damnedest to get away from C. Too simple, too many details to manage, too old and crufty, too low level. I've had intense and torrid love affairs with Java, C++, and Erlang. I've built things I'm proud of with all of them, and yet each has broken my heart. They've made promises they couldn't keep, created cultures that focus on the wrong things, and made devastating tradeoffs that eventually make you suffer painfully. And I keep crawling back to C."
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RE[5]: Point by point
by saso on Sat 12th Jan 2013 10:19 UTC in reply to "RE[4]: Point by point"
saso
Member since:
2007-04-18

Except in C, there is no way to sort anything without passing a compare function to qsort. Even an array of ints needs a hand-coded, if trivial, compare function passed to it.

Actually, the fact that qsort takes a comparator function means that it is much better than a simple sort() method on an array object. It allows you much more freedom in comparing compound and complex objects, not just primitive values. How, for instance, do you sort an array of structures/objects sensibly? The language doesn't know how, so you have to provide a comparator. This is one of the less problematic features of the standard C library - providing generic interfaces for everything. If you need your ultra-fast ultra-optimized sorter, you can always code it yourself.

Reply Parent Score: 2

RE[6]: Point by point
by ingraham on Sun 13th Jan 2013 05:23 in reply to "RE[5]: Point by point"
ingraham Member since:
2006-05-20

In Java, your class extends Comparable, then provides a definition of comparesTo(). You can now use your class with anything that wants to sort or search. You could argue the difference is just semantics or syntactic sugar. Still, the concept and syntax of function pointers is considerably more difficult to understand, and results in code that isn't as checkable by the compiler and can cause really wacky things to happen if you mess it up. In C, if I accidentally pass my string compare function to qsort while I'm trying to sort an array of ints, the program will compile and run, and then screw up badly at runtime.

Reply Parent Score: 2

RE[7]: Point by point
by kwan_e on Sun 13th Jan 2013 06:27 in reply to "RE[6]: Point by point"
kwan_e Member since:
2007-02-18

In C, if I accidentally pass my string compare function to qsort while I'm trying to sort an array of ints, the program will compile and run, and then screw up badly at runtime.


That's not so much a problem with using function pointers as it is with weak typing. qsort has to be able to sort any types, so the arguments passed to the sorting function are void*, making the function signature similarly unhelpful.

However, if you write a thin wrapper on top of qsort that takes in a function pointer with more specific argument types, then the compiler will complain reliably.

Reply Parent Score: 3

RE[7]: Point by point
by saso on Sun 13th Jan 2013 11:09 in reply to "RE[6]: Point by point"
saso Member since:
2007-04-18

I think you just consider it simpler because it's what you're used to. For instance, it would take me a good while to figure out what you said about comparesTo(), simply because I'm not used to it. Also, your example covers custom sorting of objects, but not of first class types - how do I do a custom sort on strings, or ints, or something else atomic? Sure, you could wrap the primitive types in custom object classes and incur a significant performance penalty (an array of 10000 int's is going to need 10000 malloc's and subsequent free's), in addition to adding tons of lines of code (plus a few new extra classes/files), whereas in C the problem could have been solved efficiently in about half a dozen lines of code with no extra allocation needed.

Reply Parent Score: 2