三元运营商，以“if”语句

嘿家伙，我想知道如果用如果这里声明是在时代运营商难倒代码IM有写这不使用三元运营商的一种方式：三元运营商，以“if”语句

int x1 = place.getX(); 
int x2 = x1 + 
    ((direction == direction.NORTH || direction == direction.SOUTH ? shipLength : shipWidth) - 1) * 
    (direction == direction.NORTH || direction == direction.EAST ? -1 : 1); 
int y1 = place.getY(); 
int y2 = y1 + 
    ((direction == direction.NORTH || direction == direction.SOUTH ? shipWidth : shipLength) - 1) * 
    (direction == direction.WEST || direction == direction.NORTH ? -1 : 1);

来源

2012-10-27 Indrick

是的，你可以用if/then构造来代替三元组。 – wildplasser

这里的你怎么可以把X2到状态：

int x2 = x1 + shipWidth-1; 
if(direction == direction.NORTH || direction == direction.SOUTH) 
{ 
    x2 = x1 + shipLength-1; 
} 
if (direction == direction.NORTH || direction == direction.EAST) 
{ 
    x2 = -x2; 
}

您可以应用同样的原理Y2，但三元陈述有很多清洁（我想可能有性能差异，不知道） - 我个人” d按原样使用它。

三元运算符仅仅是一个写作的条件更简单的方法，用于增加他们在线（比如这里的情况下）最有用的，语法很简单：

CONDITION ? (DO IF TRUE) : (DO IF FALSE)

它们也可以在分配使用：

int myInt = aCondition ? 1 : -1;//Makes myInt 1 if aCondition is true, -1 if false

来源

2012-10-27 12:54:59 MickMalone1983

int x1 = place.getX(); 
int x2 
if(direction == direction.NORTH || direction == direction.SOUTH){ 
    x2 = x1 + shipLength -1; 
    if(direction == direction.NORTH || direction == direction.EAST) 
     x2 *= -1; 
}else{ 
    int x2 = x1 + shipWidth-1; 
    if(direction == direction.NORTH || direction == direction.EAST) 
     x2 *= -1; 
} 

int y1 = place.getY(); 
int y2; 
if(direction == direction.NORTH || direction == direction.SOUTH){ 
    y2 = y1 + shipWidth-1; 
    if(direction == direction.NORTH || direction == direction.WEST) 
     y2 *= -1; 
}else{ 
    int y2 = y1 + shipLength-1; 
    if(direction == direction.NORTH || direction == direction.WEST) 
     y2 *= -1; 
}

我觉得三元运营商是一个很好的选择，当该语句是小，像int x = (y == 10? 1 : -1);否则代码开始不可读和问题的修正是轧花是在GNU语法的更多复杂

来源

2012-10-27 12:57:39

谢谢你似乎合乎逻辑 – Indrick

-1

以下语句是等价

condition ? a : b

和

({if (condition) 
    a; 
else 
    b;})

后者是GNU扩展，它是由大多数编译器虽然支持。第一个是简单得多写，虽然

来源

2012-10-27 13:04:24

TIL http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html – nibot

你的例子不适合我。这确实有效：'（{int x; if（condition）x = a; else x = b; x;}）'。 – nibot

一个不太通心粉版在线：

int x1 = place.getX(); 
int y1 = place.getY(); 
int x2, y2; 
switch(direction) { 
case NORTH: 
    x2 = x1-(shipLength-1); 
    y2 = y1-(shipWidth-1); 
    break; 
case SOUTH: 
    x2 = x1+(shipLength-1); 
    y2 = y1+(shipWidth-1); 
    break; 
case EAST: 
    x2 = x1-(shipWidth-1); 
    y2 = y1+(shipLength-1); 
    break; 
case WEST: 
    x2 = x1+(shipWidth-1); 
    y2 = y1-(shipLength-1); 
    break; 
default: 
    x2 = x1+(shipWidth-1); 
    y2 = y1+(shipLength-1); 
    //printf("Your ship seems to be sinking!\n"); 
    //exit(1); 
}

如果你想具体if - else if版本，上面的转换到应该是微不足道的。

来源

2012-10-27 15:32:12 hyde

三元运营商，以“if”语句

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