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Can PostgreSQL index array columns?
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Yes you can index an array, but you have to use the array operators and the GIN-index type.
Example:
CREATE TABLE "Test"("Column1" int[]);
INSERT INTO "Test" VALUES ('{10, 15, 20}');
INSERT INTO "Test" VALUES ('{10, 20, 30}');
CREATE INDEX idx_test on "Test" USING GIN ("Col...
Evaluating string “3*(4+2)” yield int 18 [duplicate]
...NET framework that can evaluate a numeric expression contained in a string and return the result? F.e.:
14 Answers
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How do I find where an exception was thrown in C++?
...t exception somewhere. All I get is a report of an exception being thrown, and no information as to where it was thrown. It seems illogical for a program compiled to contain debug symbols not to notify me of where in my code an exception was generated.
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In C, how should I read a text file and print all strings
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The simplest way is to read a character, and print it right after reading:
int c;
FILE *file;
file = fopen("test.txt", "r");
if (file) {
while ((c = getc(file)) != EOF)
putchar(c);
fclose(file);
}
c is int above, since EOF is a negative number, an...
Initialization of all elements of an array to one default value in C++?
...that you used,
int array[100] = {-1};
says "set the first element to -1 and the rest to 0" since all omitted elements are set to 0.
In C++, to set them all to -1, you can use something like std::fill_n (from <algorithm>):
std::fill_n(array, 100, -1);
In portable C, you have to roll your...
error LNK2019: 无法解析的外部符号 __imp__PlaySoundW@12，该符号在函数 \...
...W@12，该符号在函数 "long __stdcall WndProc(struct HWND__ *,unsigned int,unsigned int,long)" (?WndProc@@YGJPAUHWND__@@IIJ@Z) 中被引用#include <mmsystem.h>#pragma comment(lib, "WINMM.LIB")
#include <mmsystem.h>
#pragma comment(lib, "WINMM.LIB")
error LNK2019 PlaySound
error C2872: “count”: 不明确的符号 - C/C++ - 清泛网 - 专注C/C++及内核技术
...的符号error C2872: count: 不明确的符号 可能是conflict.cpp(4) : int count 或 C: Program Files Microsoft Visual Studio 11.0 V...error C2872: “count”: 不明确的符号
可能是“conflict.cpp(4) : int count” 或 “C:\Program Files\Microsoft Visual Studio 11.0\VC\INCLUDE\xutil...
error C2143:语法错误 : 缺少“;”(在“*”的前面) error C4430:缺少类型...
...1>d:\xxx\childfrm.h(73): error C4430: 缺少类型说明符 - 假定为 int。注意: C++ 不支持默认 int
一般这个错误是没有include头文件导致，
仔细检查下 .h 中是不是定义类成员变量时没有包含相应的头文件。
拓展：
.h中定义类对象成...
What was the strangest coding standard rule that you were forced to follow? [closed]
...this question I got almost always a definite yes you should have coding standards.
112 Answers
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Why do I need to override the equals and hashCode methods in Java?
...n conjunction with all hash-based collections, including HashMap, HashSet, and Hashtable.
Let's try to understand it with an example of what would happen if we override equals() without overriding hashCode() and attempt to use a Map.
Say we have a class like this and that two objects of MyClass are...