, and is the nether Open, upper bound closed. (Why is it so defined?) InnoDB officially defined)Here's an example from the manual to see what is Next-key lock. If the row of an index has 10,11,13,20Then the possible Next-key lock includes:(Infinity, 10](10,11](11,13](13,20](20, Infinity) (Why is infinity here not closed?) You don't get home in math ~ ~)All right,
always follow this line of thinking: I have 4 shards, so it's a very bad idea to use a 4 possible field to do the chip key.Suppose we have an application that stores user information, and each document has a continent field that represents the user's region, and its field values can be "Africa", "Antarctica", "Asia", "Australia", "Europe", "North Ameraica "or" South America ", considering that we have a data center on every continent-perhaps not Antarctica-and want to provide user data for it f
constraints: (constraints)
Location constraints: locations
Define the relationship between resources and nodes. For example, the node on which resources tend to run.
The defined range is positive infinity (INF) to negative infinity (-INF ).
Positive infinity indicates that the node runs as long as it may run on the current node. Negative
) index Sign
52 bits (0 - 51) 11 bits (50 - 62) 1 bit (63)
PrecisionAn integer (without the decimal point or exponential Notation) can contain up to 15 digits.The maximum number of decimal places is 17, but the floating point operation is not always 100% accurate:Instance
var x = 0.2+0.1; // result will be 0.30000000000000004
Octal and hexadecimalIf the prefix is 0, JavaScript interprets the numeric constant as the octal number. If the prefix is 0 and "x", it is interpreted as the hexadecimal nu
1. Basic typesThere are several basic data types for Javascript:
Number
String:
Boolean:
Undefined: When you access a non-existent variable, you get it undefined . It is also available when you define a variable but do not assign it a value undefined . JavaScript automatically initializes the variable to that value, and the undefined type has only one value undefined .
Null: means that the variable has no value or is empty.
Except for the above type, the o
e> 0, on the interval (a-r,a + R), satisfies
F (x)-a
It is said that a is the limit of f (x) on (a-r,a + R)
2) tend to the infinite function limit, defined: The function is greater than a certain "positive x" has a definition (function interval is (X, Infinity)), for all e > 0, when the |x| > x (function defined) satisfies
|f (x)-a |
3) The function limit is based on the function model, that is, a two-dimensional change process, the independent vari
One, variable1. Variable name: A combination of letters, numbers, underscores, and dollar signs that cannot begin with a number. is case sensitive. 2, declaring variables: var variable name = variable value;Second, operator1, arithmetic operators: +-*/(non-divisible)% (modulo) + +--+ = =III. Basic data types1. Basic data type: Number , string , boolean, undefined, null undefined: non-existent variablenull: No value or null value====================2. typeof returns a string of data type3, the v
number.
That is to say, a constant or infinity should be added to an infinity, and 0x7fffff + 1 will overflow. Obviously, this does not meet this basic requirement.
So we found 0x3f3f3f3f (which is the first big God to use this number). Its value is 1061109567, that is, 10 ^ 9, which is an order of magnitude higher than 0x7fffffff, it adds a constant still in the range of 32int... more importantly, an infi
back the ancient Ancient ancient Greece 2000 years ago, the age of mathematics. With the advanced prosperity of mathematics in ancient Greece, the creed of the Pythagoras school "Everything is a number" fully expresses the admiration of people. However, at that time, the number only refers to a general integer. People have always avoided the irrational number or the concept of an infinite number. FamousZhino Paradox(Zeno's paradox) not only showed people's vague understanding of
number 0, returns True
The operand is any character (including infinty) that is not 0, and returns false
The operand is null and returns True
Operand is NaN, returns true
Operand is undefined, returns true
* Multiplication
One operand is Nan, and the result is Nan
Infinity * 0 = NaN
Infinity * Non 0 = Infinity or-infinity
exponent is used, and 52 digits represent the mantissa. The IEEE floating-point values are formatted as shown in Figure 1.
Figure 1. IEEE 754 format for floating-point numbers
Because there are many ways to represent a given number in a scientific notation, you normalize the floating-point numbers so that you can use a decimal number with a base of 2 and a decimal point to the left of the dot to indicate that you need to adjust the exponent to get the numbers you want. So, for example, the
noting that although some JavaScript interpreters support the octal representation of the beginning of 0, but the ECMAScript standard is not supported, So try not to use octal notation to avoid problems with porting.Floating-point Direct volumeFloating-point direct quantities are represented as: [digits][.digits][(E|e) [(+|-)]digits], such as ①3.14, ②6.02e23, ③.22e-23//0.22x10-23Arithmetic operations in JSJS not only supports the common addition (+) minus (-) multiplication (*) except (*) and r
the return value. If the result is Nan, then the ToString () method is invoked before the preceding rule is applied. The object variable becomes a numeric variable.
Small quiz:
Perform a post increment operation on the following types of values, and what is the result?
"2″, 02DD", "", false, 22.5, + "",-false, +new Date ()
3. Addition Operation operator
The plus operator operator is also used in JavaScript for string connectors, so the rules for the plus operator are divided into two situa
used in the free software codec WavPack and DTS-HD Master Audio.
ATRAC advanced lossless is widely supported in older between man players and SonicStage version 4 or later. sonic Stage 4 allows download of ATRAC advanced lossless to minidisc players, PlayStation portable, and PlayStation 3. currently the latest administrative man players do not support ATRAC advanced lossless/ATRAC. sony has all but droppe
Sony PS VR with the mystery of the small black box is what exactly?After two years, Sony once again showed the PlayStation VR (previously called Project Morpheus) at GDC (Game Developers Conference). Sony also brought the final price of the PlayStation VR to $399 (about 2600 yuan), 44980 yen, 399 euros and 349 pounds, after Oculus Rift, HTC Vive and other star products were released. Visible, China's PS VR
than just continue to wait around, a few has decided to release their products anyway. But, without the custom-designed Steamos-back things up, the Ibuypower SBX feels half-baked. It looks like a console, but still acts like a PC, with plenty of pop-ups and errors to break the illusion for anyone Was thinking they ' d is replacing their Xbox or PlayStation. That's, if the fact that you had to use a mouse and keyboard to control the SBX didn ' t alrea
First, testingFor user agent detection, detection range includes browser engine, platform, Windows, mobile device and game system, etc./** User Agent detection script, detection range including browser engine, platform, Windows, mobile device and game system*/varClient =function(){//Rendering engine varEngine = {ie:0,//iegecko:0,//Firefoxwebkit:0,//chrome and Safarikhtml:0,//linux under the Konqueroropera:0,//operaVerNULL //Full version number};//Browser varBrowser = {ie:0, firefox:0,
First, testingFor user agent detection, detection range includes browser engine, platform, Windows, mobile device and game system, etc./** User Agent detection script, detection range including browser engine, platform, Windows, mobile device and game system*/varClient =function(){//Rendering engine varEngine = {ie:0,//iegecko:0,//Firefoxwebkit:0,//chrome and Safarikhtml:0,//linux under the Konqueroropera:0,//operaVerNULL //Full version number};//Browser varBrowser = {ie:0, firefox:0,
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