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How can I validate a string to only allow alphanumeric characters in it?
...n I validate a string using Regular Expressions to only allow alphanumeric characters in it?
10 Answers
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Base64 length calculation?
...
Each character is used to represent 6 bits (log2(64) = 6).
Therefore 4 chars are used to represent 4 * 6 = 24 bits = 3 bytes.
So you need 4*(n/3) chars to represent n bytes, and this needs to be rounded up to a multiple of 4.
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printf with std::string?
...style string, you can use the c_str() method of std::string to get a const char * that is null-terminated. Using your example:
#include <iostream>
#include <string>
#include <stdio.h>
int main()
{
using namespace std;
string myString = "Press ENTER to quit program!";
...
What does int argc, char *argv[] mean?
...ention, but they can be given any valid identifier: int main(int num_args, char** arg_strings) is equally valid.
They can also be omitted entirely, yielding int main(), if you do not intend to process command line arguments.
Try the following program:
#include <iostream>
int main(int argc,...
NULL values inside NOT IN clause
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Query A is the same as:
select 'true' where 3 = 1 or 3 = 2 or 3 = 3 or 3 = null
Since 3 = 3 is true, you get a result.
Query B is the same as:
select 'true' where 3 <> 1 and 3 <> 2 and 3 <> null
When ansi_nulls is on, 3 <&...
Difference between BYTE and CHAR in column datatypes
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Let us assume the database character set is UTF-8, which is the recommended setting in recent versions of Oracle. In this case, some characters take more than 1 byte to store in the database.
If you define the field as VARCHAR2(11 BYTE), Oracle can us...
What is the difference between static_cast and C style casting?
...situations where all that is needed is a simple conversion. The ability to select between several different casting operators of differing degrees of power can prevent programmers from inadvertently casting to an incorrect type.
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Concatenate two string literals
...tring literals using +, it is because a string literal is just an array of characters (a const char [N] where N is the length of the string plus one, for the null terminator). When you use an array in most contexts, it is converted into a pointer to its initial element.
So, when you try to do "H...
What belongs in an educational tool to demonstrate the unwarranted assumptions people make in C/C++?
...lo"); /* printf() returns the number of
characters successfully printed by it
*/
}
int World()
{
return printf("World !");
}
int main()
{
int a = Hello() + World(); //might print Hello World! or World! Hell...
Differences between C++ string == and compare()?
...ard has to say about operator==
21.4.8.2 operator==
template<class charT, class traits, class Allocator>
bool operator==(const basic_string<charT,traits,Allocator>& lhs,
const basic_string<charT,traits,Allocator>& rhs) noexcept;
Returns: lhs.compa...