[C ++ primer] Chapter 5 loop and relational expressions

1. For Loop

1. Each expression in c ++ has a value;

Int A = 0 // declaration expression

23 + 17 // Mathematical Expression

A = (B = 3) + 4 // The value of A is 7

2. Differences Between Expressions and statements

When the expression is added with ";", it is the statement.

Expression A = 10

A = 10; for statements

3. prefix and suffix

++ I; faster and more efficient than I ++;

[Note] the prefix increment (++), prefix increment (++), and unreference (*) have the same priority;

And combine rules from right to left

For example, * ++ pt; // first apply ++ to PT and then * to PT.

4. Comma Operator

The value of the comma expression is the value of the second part.

Expression: the value of I = 20, j = 30 is 30 (the value of the second part)

Cats = (I = 20, j = 30);

5. relational expressions (Relational operators: <,>, >=, =)

The priority of Relational operators is lower than that of Arithmetic Operators x + 3> the y-4 should be (x + 3)> (y-4)

The non-zero value is true, and the zero value is false.

6. Comparison of C-style strings

WORD = "mate"; array name word indicates the address of the array. constants enclosed in quotation marks are also the address of the array.

Strcpm (str1, str2); // str1 = str2 returns 0; If str1 is placed before str2 in alphabetical order, strcpm (ABC, BBC) returns a negative number.