三元運營商，以「if」語句

嘿傢伙，我想知道如果用如果這裏聲明是在時代運營商難倒代碼IM有寫這不使用三元運營商的一種方式：三元運營商，以「if」語句

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);

來源

2012-10-27 Indrick

是的，你可以用if/then構造來代替三元組。 – wildplasser

這裏的你怎麼可以把X2到狀態：

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; 
}

您可以應用同樣的原理Y2，但三元陳述有很多清潔（我想可能有性能差異，不知道） - 我個人」 d按原樣使用它。

三元運算符僅僅是一個寫作的條件更簡單的方法，用於增加他們在線（比如這裏的情況下）最有用的，語法很簡單：

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

它們也可以在分配使用：

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

來源

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; 
}

我覺得三元運營商是一個很好的選擇，當該語句是小，像int x = (y == 10? 1 : -1);否則代碼開始不可讀和問題的修正是軋花是在GNU語法的更多複雜

來源

2012-10-27 12:57:39

謝謝你似乎合乎邏輯 – Indrick

-1

以下語句是等價

condition ? a : b

和

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

後者是GNU擴展，它是由大多數編譯器雖然支持。第一個是簡單得多寫，雖然

來源

2012-10-27 13:04:24

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

你的例子不適合我。這確實有效：'（{int x; if（condition）x = a; else x = b; x;}）'。 – nibot

一個不太通心粉版在線：

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); 
}

如果你想具體if - else if版本，上面的轉換到應該是微不足道的。

來源

2012-10-27 15:32:12 hyde

三元運營商，以「if」語句

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