運(yùn)算符優(yōu)先級(jí)決定的條款在表達(dá)式中的分組。這會(huì)影響一個(gè)表達(dá)式如何計(jì)算。某些運(yùn)算符的優(yōu)先級(jí)高于其他;例如，乘法運(yùn)算符的優(yōu)先級(jí)比加法運(yùn)算符高。
例如X =7 +3* 2; 這里，x被賦值13，而不是20，因?yàn)檫\(yùn)算符*的優(yōu)先級(jí)高于+，所以它首先被乘以3 * 2，然后再加上7。
這里，具有最高優(yōu)先級(jí)的操作出現(xiàn)在表的頂部，那些具有最低出現(xiàn)在底部。在表達(dá)式中，優(yōu)先級(jí)較高的運(yùn)算符將首先計(jì)算。
| 分類(lèi) | Operator | 關(guān)聯(lián) |
|---|---|---|
| Postfix | () [] -> . ++ - - | Left to right |
| Unary | + - ! ~ ++ - - (type)* & sizeof | Right to left |
| Multiplicative | * / % | Left to right |
| Additive | + - | Left to right |
| Shift | << >> | Left to right |
| Relational | < <= > >= | Left to right |
| Equality | == != | Left to right |
| Bitwise AND | & | Left to right |
| Bitwise XOR | ^ | Left to right |
| Bitwise OR | | | Left to right |
| Logical AND | && | Left to right |
| Logical OR | || | Left to right |
| Conditional | ?: | Right to left |
| Assignment | = += -= *= /= %=>>= <<= &= ^= |= | Right to left |
| Comma | , | Left to right |
試試下面的例子就明白了在D編程語(yǔ)言中的運(yùn)算符優(yōu)先級(jí)可供選擇：
import std.stdio; int main(string[] args) { int a = 20; int b = 10; int c = 15; int d = 5; int e; e = (a + b) * c / d; // ( 30 * 15 ) / 5 writefln("Value of (a + b) * c / d is : %d ", e ); e = ((a + b) * c) / d; // (30 * 15 ) / 5 writefln("Value of ((a + b) * c) / d is : %d " , e ); e = (a + b) * (c / d); // (30) * (15/5) writefln("Value of (a + b) * (c / d) is : %d ", e ); e = a + (b * c) / d; // 20 + (150/5) writefln("Value of a + (b * c) / d is : %d " , e ); return 0; }
當(dāng)編譯并執(zhí)行上面的程序它會(huì)產(chǎn)生以下結(jié)果：
Value of (a + b) * c / d is : 90 Value of ((a + b) * c) / d is : 90 Value of (a + b) * (c / d) is : 90 Value of a + (b * c) / d is : 50
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