http://d.puremagic.com/issues/show_bug.cgi?id=5765
--- Comment #4 from bearophile_h...@eml.cc 2011-03-23 05:55:03 PDT --- (In reply to comment #3) > The thing I'm really worried about is this: > BigInt a, b, c; > > a = (a ^^ b) % c; > This is an attempt to do modular exponentiation, which comes up frequently in > cryptography. The code is mathematically correct, but completely wrong in > practice. In Python 2.6 the built-in pow function has a third optional argument, that's the modulus, that uses a more efficient algorithm to perform the powermod (note the second 6 that's not a multi-precision value): >>> (20 ** 125) % 7 6L >>> pow(20, 125, 7) 6 I suggest to add a similar function to std.math or std.bigint. Also the D compiler may recognize the (x^^y)%z pattern and replace it with a power mod function call. > So I would rather give an informative static assert for the BigInt ^^ BigInt > case. Python allows you to use the power/shift with multi-precision numbers too, if you want. The multi-precision numbers can be used transparently, syntax-wise. If you have D templated code that you want to use with both BigInt and int you will have to use a static if to change the code from x^^y to BigInt(x)^^y.toInt() (or call a little pow template function that does the same, losing infix operator syntax again), this isn't good. BitInt are meant to work as integers, mostly. I'd like a D program to work with as few changes as possible if I replace int with BigInts or BigInts with ints (in some situations I may write the code with BigInts, see the results and then try to write the same with ints/longs, to spot the overflows). -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
