Example from the standard library (core.clj:807):
(defmacro and
"Evaluates exprs one at a time, from left to right. If a form
returns logical false (nil or false), and returns that value and
doesn't evaluate any of the other expressions, otherwise it returns
the value of the last e...
section .data
msg db "Hello world!",10 ; 10 is the ASCII code for a new line (LF)
section .text
global _start
_start:
mov rax, 1
mov rdi, 1
mov rsi, msg
mov rdx, 13
syscall
mov rax, 60
mov rdi, 0
syscall
If you want to e...
You can update multiple columns in a table in the same statement, separating col=val pairs with commas:
UPDATE person
SET country = 'USA',
state = 'NY'
WHERE city = 'New York';
You can also update data in a table based on data from another table:
UPDATE person
SET state_code = cities.state_code
FROM cities
WHERE cities.city = city;
Here we are joining the person city column to the cities city column in order to get the city's state code. This is then used to updat...
Everything in .NET is an object, hence every type has ToString() method defined in Object class which can be overridden. Default implementation of this method just returns the name of the type:
public class Foo
{
}
var foo = new Foo();
Console.WriteLine(foo); // outputs Foo
ToString() is i...
Strings are immutable. You just cannot change existing string. Any operation on the string crates a new instance of the string having new value. It means that if you need to replace a single character in a very long string, memory will be allocated for a new value.
string veryLongString = ...
// m...
Despite String is a reference type == operator compares string values rather than references.
As you may know string is just an array of characters. But if you think that strings equality check and comparison is made character by character, you are mistaken. This operation is culture specific (see ...
Using GNU grep
grep -r 'pattern' <directory path>
To also list line numbers of matches use -n option
grep -rn 'pattern' <directory path>
To search only files with particular glob pattern
grep --include='*.txt' -r 'pattern' <directory path>
Exclude file patterns or direc...
Say we are working on a class representing a Person by their first and last names. We have created a basic class to do this and implemented proper equals and hashCode methods.
public class Person {
private final String lastName; //invariant - nonnull
private final String firstName; //in...
Functions and objects in different packages may have the same name. The package loaded later will 'mask' the earlier package and a warning message will be printed. When calling the function by name, the function from the most recently loaded package will be run. The earlier function can be accessed ...
In order to check whether a value is NaN, isnull() or notnull() functions can be used.
In [1]: import numpy as np
In [2]: import pandas as pd
In [3]: ser = pd.Series([1, 2, np.nan, 4])
In [4]: pd.isnull(ser)
Out[4]:
0 False
1 False
2 True
3 False
dtype: bool
Note that n...
The following command imports CSV files into a MySQL table with the same columns while respecting CSV quoting and escaping rules.
load data infile '/tmp/file.csv'
into table my_table
fields terminated by ','
optionally enclosed by '"'
escaped by '"'
lines terminated by '\n'
ignore 1...
The option -v followed by an assignment of the form variable=value can be used to pass parameters to an awk program. This is illustrated by the punishment program below, whose job is to write count times the sentence “I shall not talk in class.” on standard output. The following example uses the v...
// Checks a string to see if it is a palindrome
bool function IsPalindrome(string input) {
if (input.size() <= 1) {
return true;
}
else if (input[0] == input[input.size() - 1]) {
return IsPalindrome(input.substr(1,input.size() - 2));
}
else {
r...
Custom events usually need custom event arguments containing information about the event. For example MouseEventArgs which is used by mouse events like MouseDown or MouseUp events, contains information about Location or Buttons which used to generate the event.
When creating new events, to create a...
A cancelable event can be raised by a class when it is about to perform an action that can be canceled, such as the FormClosing event of a Form.
To create such event:
Create a new event arg deriving from CancelEventArgs and add additional properties for event data.
Create an event using EventH...
