tuples

问题 The boost::mpl algorithms seem not to be able to work on std::tuple types out of the box, e.g., the following does not compile (boost-1.46.0, g++ snapshot 2011-02-19): #include <tuple> #include <boost/mpl/vector.hpp> #include <boost/mpl/contains.hpp> namespace mpl=boost::mpl; typedef mpl::vector<int,float,bool> types; static_assert(mpl::contains<types, float>::value, "vector contains bool"); typedef std::tuple<int,float,bool> types2; // the following does not compile: // error: no class

问题 This question already has answers here : compare object to empty tuple with the 'is' operator in Python 2.x (4 answers) Closed 2 years ago . I want to make my code more (memory-)efficient. Right now we have a lot of functions that take an iterable as parameter like: def foo(para,meter,iterable): #... pass and sometimes we have to provide it an empty list to do its work properly: foo(14,25,[]) . The problem is that each time a new list is constructed: it requires to allocate on the heap, and a

问题 This question already has answers here : compare object to empty tuple with the 'is' operator in Python 2.x (4 answers) Closed 2 years ago . I want to make my code more (memory-)efficient. Right now we have a lot of functions that take an iterable as parameter like: def foo(para,meter,iterable): #... pass and sometimes we have to provide it an empty list to do its work properly: foo(14,25,[]) . The problem is that each time a new list is constructed: it requires to allocate on the heap, and a

问题 Is there any limit to maximum row of table in DBMS (specially MySQL)? I want create table for saving logfile and it's row increase so fast I want know what shoud I do to prevent any problem. 回答1: You should periodically move log rows out to a historical database for data mining and purge them from the transactional database. It's a common practice. 回答2: I don't think there is an official limit, it will depend on maximum index sizes and filesystem restrictions. From mySQL 5.0 Features: Support

问题 scala> val set = scala.collection.mutable.Set[(Int, Int)]() set: scala.collection.mutable.Set[(Int, Int)] = Set() scala> set += (3, 4) <console>:9: error: type mismatch; found : Int(3) required: (Int, Int) set += (3, 4) ^ scala> set += Tuple2(3, 4) res5: set.type = Set((3,4)) Adding (3, 4) does not work - why ? Normally, (3, 4) also represents a tuple with two elements. 回答1: The issue is that it exists in the Set trait a method +(elem1: A, elem2: A, elems: A+) and the compiler is confused by

问题 I would like to access csv files in scala in a strongly typed manner. For example, as I read each line of the csv, it is automatically parsed and represented as a tuple with the appropriate types. I could specify the types beforehand in some sort of schema that is passed to the parser. Are there any libraries that exist for doing this? If not, how could I go about implementing this functionality on my own? 回答1: product-collections appears to be a good fit for your requirements: scala> val

问题 I would like to access csv files in scala in a strongly typed manner. For example, as I read each line of the csv, it is automatically parsed and represented as a tuple with the appropriate types. I could specify the types beforehand in some sort of schema that is passed to the parser. Are there any libraries that exist for doing this? If not, how could I go about implementing this functionality on my own? 回答1: product-collections appears to be a good fit for your requirements: scala> val

问题 http://www.erlang.org/news/35 mentioned that this will be documented, but I can't find it in the documentation. 回答1: A "tuple module" is a tuple with two elements, the name of a module and a list of extra arguments. For example: {my_module, [foo, bar]} Such a tuple can be used instead of a module name in function calls. In this case, the function being called will get the tuple in question as an additional argument at the end of the argument list: 3> Module = {lists, [[foo]]}. {lists,[[foo]]}

问题 http://www.erlang.org/news/35 mentioned that this will be documented, but I can't find it in the documentation. 回答1: A "tuple module" is a tuple with two elements, the name of a module and a list of extra arguments. For example: {my_module, [foo, bar]} Such a tuple can be used instead of a module name in function calls. In this case, the function being called will get the tuple in question as an additional argument at the end of the argument list: 3> Module = {lists, [[foo]]}. {lists,[[foo]]}

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 4 days ago . i have a list of tuple like this seq=[((), ('2',)), (('0', '1'), ('1', '4')), (('0', '2'), ('2', '0')), (('0', '2'), ('2', '4')),(('0', '4'), ('4', '0')), (('0', '4'), ('4', '2')), (('1', '2'), ('2', '4')), (('1', '4'), ('4', '1')), (('2',), ('2', '0')), (('2', '0'), ('0', '2')), (