運算符優先級

運算符優先級工具是一种帮助程序員确定計算表达式中各个運算符優先級的工具。

C++運算符優先級
Precedence	Operator	Description	Associativity
1	`::`	Scope resolution	Left-to-right
2	`++` `--`	Suffix/postfix increment and decrement
	`()`	Function call
	`[]`	Array subscripting
	`.`	Element selection by reference
	`?>`	Element selection through pointer
3	`++` `--`	Prefix increment and decrement	Right-to-left
	`+` `?`	Unary plus and minus
	`!` `~`	Logical NOT and bitwise NOT
	`(type)`	Type cast
	`*`	Indirection (dereference)
	`&`	Address-of
	`sizeof`	Size-of
	`new`, `new[]`	Dynamic memory allocation
	`delete`, `delete[]`	Dynamic memory deallocation
4	`.` `->`	Pointer to member	Left-to-right
5	`*` `/` `%`	Multiplication, division, and remainder
6	`+` `?`	Addition and subtraction
7	`<<` `>>`	Bitwise left shift and right shift
8	`<` `<=`	For relational operators < and ≤ respectively
8	`>` `>=`	For relational operators > and ≥ respectively
9	`==` `!=`	For relational = and ≠ respectively
10	`&`	Bitwise AND
11	`^`	Bitwise XOR (exclusive or)
12	`\|`	Bitwise OR (inclusive or)
13	`&&`	Logical AND
14	`\|\|`	Logical OR
15	`?:`	Ternary conditional	Right-to-Left
16	`=`	Direct assignment (provided by default for C++ classes)
	`+=` `?=`	Assignment by sum and difference
	`*=` `/=` `%=`	Assignment by product, quotient, and remainder
	`<<=` `>>=`	Assignment by bitwise left shift and right shift
	`&=` `^=` `\|=`	Assignment by bitwise AND, XOR, and OR
17	`throw`	Throw operator (for exceptions)
18	`,`	Comma	Left-to-right

C语言運算符優先級
Precedence	Operator	Description	Associativity
1	`++` `--`	Suffix/postfix increment and decrement	Left-to-right
	`()`	Function call
	`[]`	Array subscripting
	`.`	Structure and union member access
	`?>`	Structure and union member access through pointer
	`(type){list}`	Compound literal(C99)
2	`++` `--`	Prefix increment and decrement	Right-to-left
	`+` `?`	Unary plus and minus
	`!` `~`	Logical NOT and bitwise NOT
	`(type)`	Type cast
	`*`	Indirection (dereference)
	`&`	Address-of
	`sizeof`	Size-of
	`_Alignof`	Alignment requirement(C11)
3	`*` `/` `%`	Multiplication, division, and remainder	Left-to-right
4	`+` `?`	Addition and subtraction
5	`<<` `>>`	Bitwise left shift and right shift
6	`<` `<=`	For relational operators < and ≤ respectively
6	`>` `>=`	For relational operators > and ≥ respectively
7	`==` `!=`	For relational = and ≠ respectively
8	`&`	Bitwise AND
9	`^`	Bitwise XOR (exclusive or)
10	`\|`	Bitwise OR (inclusive or)
11	`&&`	Logical AND
12	`\|\|`	Logical OR
13	`?:`	Ternary conditional	Right-to-Left
14	`=`	Simple assignment
	`+=` `?=`	Assignment by sum and difference
	`*=` `/=` `%=`	Assignment by product, quotient, and remainder
	`<<=` `>>=`	Assignment by bitwise left shift and right shift
	`&=` `^=` `\|=`	Assignment by bitwise AND, XOR, and OR
15	`,`	Comma	Left-to-right

PHP運算符優先級
結合方向	運算符	附加信息
非結合	`clone new`	clone 和 new
左	`[`	array()
非結合	`++ --`	递增／递减運算符
非結合	`~ - (int) (float) (string) (array) (object) (bool) @`	類型
非結合	`instanceof`	類型
右結合	`!`	邏輯操作符
左	`* / %`	算术運算符
左	`+ - .`	算术運算符和字符串運算符
左	`<< >>`	位運算符
非結合	`< <= > >= <>`	比較運算符
非結合	`== != === !==`	比較運算符
左	`&`	位運算符和引用
左	`^`	位運算符
左	`\|`	位運算符
左	`&&`	逻辑運算符
左	`\|\|`	逻辑運算符
左	`? :`	三元運算符
右	`= += -= *= /= .= %= &= \|= ^= <<= >>=`	赋值運算符
左	`and`	逻辑運算符
左	`xor`	逻辑運算符
左	`or`	逻辑運算符
左	`,`	多處用到

这个表给出Python的運算符優先級（从低到高）.

从最低的優先級（最松散地结合）到最高的優先級（最紧密地结合）。

这意味着在一个表达式中，Python会首先計算表中较下面的運算符，然后在計算列在表上部的運算符。