Predicates that produce side effects leave the realm of pure logic. These are for example:
writeq/1
read/1
format/2
Side effects are phenomena that cannot be reasoned about within the program. For example, deletion of a file or output on the system terminal.
Predicates that reason about instantiations are called meta-logical. Examples are:
var/1
ground/1
integer/1
These predicates are outside the realm of pure monotonic logic programs, because they break properties like commutativity of conjunction.
Other predicates that are meta-logical includ...
In oracle, the difference (in days and/or fractions thereof) between two DATEs can be found using subtraction:
SELECT DATE '2016-03-23' - DATE '2015-12-25' AS difference FROM DUAL;
Outputs the number of days between the two dates:
DIFFERENCE
----------
89
And:
SELECT TO_DATE( '201...
The MEDIAN function since Oracle 10g is an easy to use aggregation function:
SELECT MEDIAN(SAL)
FROM EMP
It returns the median of the values
Works on DATETIME values too.
The result of MEDIAN is computed by first ordering the rows. Using N as the number of rows in the group, Oracle calcula...
Sometimes, we may open a file which we do not have permission to write in Vim without using sudo.
Use this command to save a read-only file edited in Vim.
:w !sudo tee > /dev/null %
Which you could map to :w!! in your .vimrc:
cmap w!! w !sudo tee > /dev/null %
You will be presented a ...
There are many situation where you want to draw an image that is rotated, scaled, and translated. The rotation should occur around the center of the image. This is the quickest way to do so on the 2D canvas. These functions a well suited to 2D games where the expectation is to render a few hundred e...
Redirect any naked domain to www.[your_domain].tld:
# Start Apache Rewriting engine
RewriteEngine On
# Make sure you're not already using www subdomain
# and that the host string is not empty
RewriteCond %{HTTP_HOST} !^$
RewriteCond %{HTTP_HOST} !^www\.
# We check for http/https connection ...
Bash indirection permits to get the value of a variable whose name is contained in another variable. Variables example:
$ red="the color red"
$ green="the color green"
$ color=red
$ echo "${!color}"
the color red
$ color=green
$ echo "${!color}"
the ...
1. URLByDeletingPathExtension:
If the receiver represents the root path, this property contains a copy of the original URL. If the URL has multiple path extensions, only the last one is removed.
2. URLByAppendingPathExtension:
Returns a new URL made by appending a path extension to the original U...
Creates a image representing a linear gradient of colors.
linear-gradient( 0deg, red, yellow 50%, blue);
This creates a gradient going from bottom to top, with colors starting at red, then yellow at 50%, and finishing in blue.
Following example illustrate the simplest Hello World in groovy using script, place the following code snippet in a file, say helloWorld.groovy
println 'Hello World!'
How to execute:
In the command line, groovy helloWorld.groovy
Output:
Hello World!
Commands have one input (STDIN) and two kinds of outputs, standard output (STDOUT) and standard error (STDERR).
For example:
STDIN
root@server~# read
Type some text here
Standard input is used to provide input to a program.
(Here we're using the read builtin to read a line from STDIN.)
STDO...
Media queries have an optional mediatype parameter. This parameter is placed directly after the @media declaration (@media mediatype), for example:
@media print {
html {
background-color: white;
}
}
The above CSS code will give the DOM HTML element a white background color wh...
Any predicate function can be used as a spec. Here's a simple example:
(clojure.spec/valid? odd? 1)
;;=> true
(clojure.spec/valid? odd? 2)
;;=> false
the valid? function will take a spec and a value and return true if the value conforms to the spec and false otherwise.
One other inte...
Suppose we have an interface:
interface IPerson {
name: string;
age: number;
breath(): void;
}
And we want to create more specific interface that has the same properties of the person, we can do it using the extends keyword:
interface IManager extends IPerson {
managerId:...
Install jquery via npm :
npm install jquery --save
Install typings for the library:
To add typings for a library, do the following:
typings install jquery --global --save
Add jquery to angular-cli-build.js file to vendorNpmFiles array:
This is required so the build system...
