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STL中map容器使用自定义key类型报错详解 - C/C++ - 清泛网 - 专注C/C++及内核技术
...写测试代码定义一个结构体来试试：[cpp]view plaincopystructa{char*pName;intm_a;} 引言
STL的map容器中，key的类型是不是随意的呢？
实践
编写测试代码
定义一个结构体来试试：
struct a
{
char* pName;
int m_a;
};
...
map<a, i...
What is a good Hash Function?
... that differ only in the last 4 bytes can collide easily. If you have a 30 character string, that differ in the last 4 bytes, after 28 bytes have been processes, the hashes differ only in the last 2 bytes. That means you are GUARANTEED a collision for one of the remaining two-byte values. (Yeah, it'...
How to develop a soft keyboard for Android? [closed]
... is showing in setting option with built in keyboard, but in actual when i select my custom keyboard to replace inbuilt keyboard my app in crashing. Do you have any idea where i am going wrong?
– Aniket
Oct 10 '13 at 9:39
...
Implement touch using Python?
...'atime', c_timespec), ('mtime', c_timespec)]
utimens = CFUNCTYPE(c_int, c_char_p, POINTER(c_utimbuf))
futimens = CFUNCTYPE(c_int, c_char_p, POINTER(c_utimbuf))
# from /usr/include/i386-linux-gnu/bits/stat.h
UTIME_NOW = ((1l << 30) - 1l)
UTIME_OMIT = ((1l << 30) - 2l)
now = c_timespe...
When should I use Struct vs. OpenStruct?
....new(:data1, :data2)
n = Newtype.new
C:
typedef struct {
int data1;
char data2;
} newtype;
newtype n;
The OpenStruct class can be compared to an anonymous struct declaration in C. It allows the programmer to create an instance of a complex type.
Ruby:
o = OpenStruct.new(data1: 0, data2:...
Why is it impossible to build a compiler that can determine if a C++ function will change the value
... /* modify variable */
variable = 1;
}
}
int main(int argc, char **argv) {
if (modifies_variable(f, variable)) {
printf("Modifies variable\n");
} else {
printf("Does not modify variable\n");
}
return 0;
}
...
Is there a good reason I see VARCHAR(255) used so often (as opposed to another length)?
...n multiple courses, books, and jobs, I have seen text fields defined as VARCHAR(255) as kind of the default for "shortish" text. Is there any good reason that a length of 255 is chosen so often, other than being a nice round number ? Is it a holdout from some time in the past when there was a goo...
Polymorphism in C++
...egorise them in various ways:
When is the polymorphic type-specific code selected?
Run time means the compiler must generate code for all the types the program might handle while running, and at run-time the correct code is selected (virtual dispatch)
Compile time means the choice of type-specif...
What are the underlying data structures used for Redis?
...m-ish unique users") or with replacement ("give me 7 cards, but after each selection, put the card back so it can potentially be sampled again").
For all possible operations on sets, see the sets docs.
Sorted Sets
Redis sorted sets are sets with a user-defined ordering.
For simplicity, you can think...
Python json.loads shows ValueError: Extra data
..., end, len(s)))
ValueError: Extra data: line 1 column 3 - line 1 column 5 (char 2 - 4)
If you want to dump multiple dictionaries, wrap them in a list, dump the list (instead of dumping dictionaries multiple times)
>>> dict1 = {}
>>> dict2 = {}
>>> json.dumps([dict1, dic...