Ternary operator vs if else

Question

In C    is the    operator faster than if     else statements  Are there any differences between them in compiled code

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I ve seen GCC turn the conditional operator into cmov  conditional move  instructions  while turning if statements into branches  which meant in our case  the code was faster when using the conditional operator  But that was a couple of years ago  and most likely today  both would compile to the same code   There s no guarantee that they ll compile to the same code  If you need the performance then  as always  measure  And when you ve measured and found out that 1  your code is too slow  and 2  it is this particular chunk of code that is the culprit  then study the assembly code generated by the compiler and check for yourself what is happening   Don t trust golden rules like  the compiler will always generate more efficient code if I use the conditional operator

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Depends on your compiler  but on any modern compiler there is generally no difference  It s something you shouldn t worry about  Concentrate on the maintainability of your code

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Regardless the compiled code  They are semantically different thing   lt cond gt   lt true expr gt   lt false expr gt  is an expression and if  else   is a statement   Although the syntax of conditional expression seems awkward  it is a good thing  You are forced to provide a  lt false expr gt  and the two expressions are type checked   The equivalent to if  else   in expression-based  functional language like Lisp  Haskell is     in C    instead of if  else   statement

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It is not faster  There is one difference when you can initialize a constant variable depending on some expression   const int x    a lt b    b   a    You can t do the same with if-else

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During reversing some code  which I don t remember  few years ago  I saw single line difference between the Machine Code of    and if-else  Don t remember much but it is clear that implementation of both is different   But I advise You to not choose one of them b coz of its efficiency  choose according to readability of code or your convenience  Happy Coding

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I think that there are situations where the inline if can yield  faster  code because of the scope it works at  Object creation and destruction can be costly so consider the follow scenario    class A      public      A     value 0            cout  lt  lt   Default ctor   lt  lt  endl            A int myInt    value myInt                cout  lt  lt   Overloaded ctor   lt  lt  endl             A amp  operator  const A amp  other           cout  lt  lt     operator   lt  lt  endl          value   other value               A            cout  lt  lt   destroyed   lt  lt  std  endl             int value        int main                 A a         if true              a   A 5           else             a   A 10                     cout  lt  lt   Next test   lt  lt  endl               A b   true  A 5    A 10           return 0      With this code  the output will be    Default ctor                                                                                                                                                                                                                       Overloaded ctor                                                                                                                                                                                                                      operator                                                                                                                                                                                                                         destroyed                                                                                                                                                                                                                          destroyed                                                                                                                                                                                                                          Next test                                                                                                                                                                                                                          Overloaded ctor                                                                                                                                                                                                                    destroyed     So by inlining the if  we save a bunch of operation needed to keep a alive at the same scope as b  While it is highly probable that the condition evaluation speed is pretty equal in both scenarios  changing scope forces you to take other factors into consideration that the inline if allows you to avoid

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No  they are converted to exactly the same executable code

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Ternary Operator always returns a value  So in situation when you want some output value from result and there are only 2 conditions always better to use ternary operator  Use if-else if any of the above mentioned conditions are not true

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Now I can t help you with that  I may be able to help with a secondary question beneath it  do I want to use it  If you just want to know of the speed  just ignore my comment   All I can say is please be very smart about when to use the ternary     operator  It can be a blessing as much as a curse for readability    Ask yourself if you find this easier to read before using it  int x   x    1   x   1   x   1   if  x    1       x   1   else      x   2    if  x    1      x   1 else     x   1   Yes It looks stupid to make the code 100  bogus  But that little trick helped me analyse my readability of code  It s the readability of the operator you look at in this sample  and not the content    It LOOKS clean  but so does the average toilet seat and doorknob  In my experience  which is limited  I have seen very little people actually being able to quickly extradite information required from a ternary operator  avoid unless 100  sure it s better  It s a pain to fix when it s bugged aswell I think

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I would expect that on most compilers and target platforms  there will be cases where  if  is faster and cases where    is faster   There will also be cases where one form is more or less compact than the other   Which cases favor one form or the other will vary between compilers and platforms   If you re writing performance-critical code on an embedded micro  look at what the compiler is generating in each case and see which is better   On a  mainstream  PC  because of caching issues  the only way to see which is better is to benchmark both forms in something resembling the real application

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Just to be a bit left handed     x   y   x   value   will assign value to y if x is not 0  false

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In C A ternary operator         is available to construct conditional expressions of the form   exp1   exp2 exp3   where exp1 exp2 and exp3 are expressions  for Example           a 20          b 25          x  a gt b  a b           in the above example x value will be assigned to b    This can be written  using if  else statement as follows              if  a gt b               x a               else              x b      Hence there is no difference between these two  This for the programmer to write easily  but for compiler both are same

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They are the same  however  the ternary operator can be used in places where it is difficult to use a if else   printf  Total   d item s   cnt  cnt    1    s           Doing that statement with an if else  would generate a very different compiled code     Update after 8 years     Actually  I think this would be better   printf cnt    1    Total   d item     Total   d items   cnt      actually  I m pretty sure you can replace the   d  in the first string with  one

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You are not forced to put it all on one line -  x   y  1       2         else     3    It is much clearer than if else because you can see immediately that both branches lead to x being assigned to

[c++] Ternary operator ?: vs if...else

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