Ever wish you could just write C and C++ code in GAP? Well now you can, with the gapcpp package from: https://github.com/ChrisJefferson/gapcpp

After running './configure' in the packages directory and loading it, you will find one method, 'CompileMethod', which accepts C++ (or C) code, the name of your function and it's number of arguments. The function is then automatically linked into GAP, and GAP types turned into C++ types (and vice versa). Here's an easy example: gap> fun := CompileMethod("int f(int X) { return X; }", "f", 1);; gap> fun(3); 3 That's fairly boring however. Let's consider something more interesting! Perhaps we want to sort a list of integers by their last digit: gap> SortBy([1..1000000], x -> x mod 10);; gap> time; 548 Hmm.. Lets give that 'mod' function some C++ power! gap> m := CompileMethod("int f(int X) { return X % 10; }", "f", 1);; gap> SortBy([1..1000000], m);; gap> time 487 Hmm, a little speedup, but not as much as we would like. Let's push the whole thing into C++, using new 'triple quotes' to make the code easier to write (in the master branch of GAP, not package specific!) gap> x := CompileMethod(""" bool comp(int i, int j) { return i%10 < j%10; } std::vector<int> sb(std::vector<int> i) { std::sort(i.begin(), i.end(),comp); return i; }""", "sb", 1); gap> x([1..1000000]);; gap> time; 48 Wow, 10x speedup! Of course, C++ lets us do new things. Perhaps we really wish we had a stable sort? No problem! gap> x := CompileMethod(""" bool comp(int i, int j) { return i%10 < j%10; } std::vector<int> sb(std::vector<int> i) { std::stable_sort(i.begin(), i.end(),comp); return i; }""", "sb", 1); gap> x([1..1000000]);; gap> time; 124 A little slower, but with the bonus of being stable! Let's try some more things: gap> PartialSums([1..50000]);; gap> time; 26021 gap> x := CompileMethod(""" #include <numeric> std::vector<int> sums(std::vector<int> v) { std::vector<int> out(v.size()); // r means 'reverse', we do this to agree with GAP's order std::partial_sum(v.rbegin(), v.rend(), out.rbegin()); return out; }""", "sums", 1);; gap> PartialSums([1..50000]);; gap> time; 1 The following C++ types are currently supported (recursively). More types can be added on request! std::vector std::list std::deque std::pair std::string int Bool vec1 (a custom vector type which is 1-indexed, for each GAP<->C++ integration) optional (a way of marking missing values, so std::vector<optional<int> > supports lists with missing values, unlike std::vector<int>) If you understand GAP, You can also use Obj and all the normal GAP method to access objects. There is also initial support for gap records (see the tests for examples). I am interested in any requests for improvements, or usage of this package (or wished usages of this package). Chris _______________________________________________ Forum mailing list Forum@mail.gap-system.org http://mail.gap-system.org/mailman/listinfo/forum