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#define Aspect_ratio 1.653The compiler will never see aspect_ratio this symbol name, because before the source code into the compiler, it will be removed by the preprocessor, so aspect_ratio will not be added to the list of symbols. If the code

1) #define是preprocessing Directives, which is performed when the preprocessing is compiledsimple substitution, no correctness check, whether the meaning is correct or not, only when compiling the source program has been expanded to find possible

This article to share the content is to use PHP code to write ️ and their own definition of text, has a certain reference value, the need for friends can refer to ";

1 , Syntax Statement: Parameter xx = YY;'Define XX YY Usage: Xx'Xx2 , Scope Parameter The file to be declared; 'Define It is valid from the time the compiler reads this instruction to the end of compilation, or 'Undef Command to make it

Str1.equals (str2) to judge, cannot use = or! = To determine the reason: Because string is of the reference type rather than the basic data type, their comparison uses the address and value (equivalent to the pointer in C) for comparison, because

Typedef char * string_t; # define string_d char * // # define string_d char * is a simple replacement? Typedef char * string_t defines a new type. // The main difference is that string_t a, B; string_d C, D; A, B, and C are all char * types, D is of

I tried it myself, no ah, how to do? Reply to discussion (solution) Is this what the landlord said?Class aa{Public $name;}Class bb{function Testaa (AA $a) {$a->age=333;}}$AA =new AA ();$BB =new BB ();$BB->testaa ($AA);Echo $aa->age;

Try to use const and inline instead of # define This clause is best referred to as "try to use the compiler instead of preprocessing", because # define is often considered not part of the language itself. This is one of the problems. Let's look at

If we have in the operation of personal blog, or often like to other people's blog visit, leave a message, will certainly see a variety of users visit the head, some of the head or more characteristics have personality, and can attract us to pay

Recently in looking at MySQL source code, which is a C + + grammar forgotten to light up, review the basic grammatical structure, easy to understand the source code. Of course for, often in the case of C + +, These grammars are very

1. Grammar Statement: Parameter data = 8 ' D14; ' Define Data 8 ' D14 Use:Data ' Data 2. Scope Parameter the file that acts on the Declaration, ' define reads from the compiler until the end of the compilation is valid, or the ' undef command

SQL constraints (Constraints)Constraints are used to restrict the type of data that is joined to a table.You can specify constraints (through the CREATE TABLE statement) When you create the table, or you can (via the ALTER table statement) after the

SQL PRIMARY KEY ConstraintThe PRIMARY KEY constraint uniquely identifies each record in a database table.The primary key must contain a unique value.Primary key columns cannot contain NULL values.Each table should have a primary key, and each table

Introduction This article introduces a good small open-source project: webviewjavascriptbridge. It elegantly implements intercommunication between JS and iOS objc nativecode when uiwebview is used. It supports message sending, receiving, message

Original address: http://www.manongjc.com/article/491.html Const is the definition of a class member constant, which cannot be changed after the definition, and define we define global constants so that we can access them elsewhere but not change

SQL Advanced (3) SQL SELECT INTO statement the SQL SELECT INTO statement can be used to create a backup copy of the table.The SELECT INTO statement SELECT INTO statement selects data from one table and then inserts the data into another table.The

The SQL SELECT into statement can be used to create a backup copy of the table.SELECT into statementThe SELECT INTO statement selects data from one table and then inserts the data into another table.The SELECT into statement is commonly used to

1. Compile a program, input three numbers from the keyboard, and use the if statement and logical expression to find the maximum number.2. Compile a program, input three numbers from the keyboard, and use the if statement and logical expression to

A constant is an identifier (first name) of a simple value. As the name implies, the value cannot be changed during script execution (except for the so-called magic constants, they are not constants). Changshime is considered to be case sensitive.

Net Framework developer Guide   The following sections describe the. NET Framework regular expression class. Regex The Regex class indicates an unchangeable (read-only) Regular Expression class. It also contains various static methods that