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I encountered a line of code:
int a = 10;
int b = 40;
a = a + b - (b = a);
cout << a << " " << b << endl;
I cannot understand what happens in this code. Can anyone explain for me?
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It is also possible to declare a variable and assign it a value in the same line, so instead of int i and then i = 9 you can write int i = 9 all in one go. If you have more than one variable of the same type you can also declare them together e.g.
An assignment statement always has a single variable on the left hand side. The value of the expression (which can contain math operators and other variables) on the right of the = sign is stored in the variable on the left.
In Java, an assignment statement is an expression that evaluates a value, which is assigned to the variable on the left side of the assignment operator. Whereas an assignment expression is the same, except it does not take into account the variable.
A variable is a string of characters and numbers associated with a piece of information. The assignment operator, denoted by the “=” symbol, is the operator that is used to assign values to variables in Python. The line x=1 takes the known value, 1, and assigns that value to the variable with name “x”.
Undefined behavior. the value of b is changed and used for computation without an intervening sequence point. The results of the program are unpredictable - it can print anything or crash, or do do some nasty system calls.
Except where noted, the order of evaluation of operands of individual operators and subexpressions of individual expressions, and the order in which side effects take place, is unspecified.53) Between the previous and next sequence point a scalar object shall have its stored value modified at most once by the evaluation of an expression. Furthermore, the prior value shall be accessed only to determine the value to be stored. The requirements of this paragraph shall be met for each allowable ordering of the subexpressions of a full expression; otherwise the behavior is undefined.
160
Undefined behavior
http://en.wikipedia.org/wiki/Sequence_point
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