declaration

java class declaration <T>

由 北城以北 提交于 2019-11-30 18:02:24
问题 I'm familiar with simple class declaration public class test but I don't understand public class test<T> . 回答1: < T > refers to a generic type. Generic types are introduced in Java to provide you with compile time, and this is important due to type erasure, type-safety. It's especially useful in Collections because it frees you from manual casting. It is a good idea to read more on generics, especially the documentation on the topic by Angelika Langer is very good: http://www.angelikalanger

What's the benefit for a C source file include its own header file

由 谁说我不能喝 提交于 2019-11-30 17:48:35
I understand that if a source file need to reference functions from other file then it needs to include its header file, but I don't understand why the source file include its own header file. Content in header file is simply being copied and pasted into the source file as function declarations in per-processing time. For source file who include its own header file, such "declaration" doesn't seem necessary to me, in fact, project still compile and link no problem after remove the header from it's source file, so what's the reason for source file include its own header? The main benefit is

Difference between local allocatable and automatic arrays

由 痞子三分冷 提交于 2019-11-30 17:40:38
问题 I am interested in the difference between alloc_array and automatic_array in the following extract: subroutine mysub(n) integer, intent(in) :: n integer :: automatic_array(n) integer, allocatable :: alloc_array(:) allocate(alloc_array(n)) ...[code]... I am familiar enough with the basics of allocation (not so much on advanced techniques) to know that allocation allows you to change the size of the array in the middle of the code (as pointed out in this question), but I'm interested in

Simple C array declaration / assignment question

由 匆匆过客 提交于 2019-11-30 16:58:49
问题 In higher level languages I would be able something similar to this example in C and it would be fine. However, when I compile this C example it complains bitterly. How can I assign new arrays to the array I declared? int values[3]; if(1) values = {1,2,3}; printf("%i", values[0]); Thanks. 回答1: you can declare static array with data to initialize from: static int initvalues[3] = {1,2,3}; … if(1) memmove(values,initvalues,sizeof(values)); 回答2: You can only do multiple assignment of the array,

PHP: how to avoid redeclaring functions?

由 。_饼干妹妹 提交于 2019-11-30 16:49:59
I tend to get errors such as: Fatal error: Cannot redeclare get_raw_data_list() (previously declared in /var/www/codes/handlers/make_a_thread/get_raw_data_list.php:7) in /var/www/codes/handlers/make_a_thread/get_raw_data_list.php on line 19 how can I avoid the error? Is it possible to create a IF-clause to check whether a function is declared before declaring it? Use require_once or include_once as opposed to include or require when including the files that contain your functions. The _once siblings of include and require will force PHP to check if the file has already been included/required,

Where ampersand “&” can be put when passing argument by reference?

由 若如初见. 提交于 2019-11-30 16:42:52
问题 In the examples that I saw the arguments were passed by reference in the following way: void AddOne(int &y) In the code that I have I see the following syntax: void AddOne(int& y) I wonder if it is the same or the second case is somehow different from the first one. 回答1: Both are exactly the same. No difference at all. All that matters is that & should be between the type and the variable name. Spaces don't matter. So void AddOne(int& y); void AddOne(int &y); void AddOne(int & y) void AddOne

is this a variable or function

由 房东的猫 提交于 2019-11-30 16:36:23
I was just looking through implementation of non local means algorithm via google (thanks google for code search) and come across this function mirror. template<typename T,typename U,bool N> inline int boundaryExpansion::helperBase<T,U,N>::mirror(const int src, const int size, const int last) const { const int32 alpha(src%size); if (alpha>=0) { return (((src/size) & 0x00000001) != 0) ? last-alpha : alpha; } return (((src/size) & 0x00000001) == 0) ? -alpha-1 : size+alpha; } And the line I am interested in is this const int32 alpha(src%size); Now what is alpha here? A function or a variable?

Why is it possible to declare a struct and a non-struct with the same name?

由 隐身守侯 提交于 2019-11-30 15:35:20
问题 Apparently, For reasons that reach into the prehistory of C, it is possible to declare a struct and a non-struct with the same name in the same scope. - ( Bjarne Stroustrup - The C++ Programming Language. 4th Edition ) For example: struct Ambig {}; // the struct must be referred to with the prefix struct void Ambig(struct Ambig* buf) {} I'm just curious what the initial reason was? Without understanding, it seems like an example of bad language design, that causes ambiguity and is confusing.

is this a variable or function

由 只谈情不闲聊 提交于 2019-11-30 14:23:52
问题 I was just looking through implementation of non local means algorithm via google (thanks google for code search) and come across this function mirror. template<typename T,typename U,bool N> inline int boundaryExpansion::helperBase<T,U,N>::mirror(const int src, const int size, const int last) const { const int32 alpha(src%size); if (alpha>=0) { return (((src/size) & 0x00000001) != 0) ? last-alpha : alpha; } return (((src/size) & 0x00000001) == 0) ? -alpha-1 : size+alpha; } And the line I am

Function Pointer Declaration - what does __P do?

由 扶醉桌前 提交于 2019-11-30 13:39:56
The usual form of function pointer definitions is: int function(int, int); int (*ptr)(int, int); but I saw a form today which I didn't understand. Can anyone explain this please? int (*close) __P((struct __db *)); The __P() macro is usually used to support C implementations from the days of K&R C, when there were no prototypes (which were introduced to C with C89). Basically the logic is #if SOME_LOGIC_TO_TEST_WHETHER_IMPLEMENTATION_SUPPORTS_PROTOTYPES # define __P(argument_list) argument_list #else # define __P(argument_list) () #endif Can you see how this works when applied to your example?
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