pre-increment

I've just encountered a 'feature' in Javascript regarding pre-increments. In all other languages I've used, it goes like I thought it would. E.g. in C++: #include <iostream> int main() { int i = 0; i += ++i; std::cout << i << std::endl; // Outputs 2. } So, ++i doesn't make copy of the variable, hence the output is 2. Same in PHP: <?php $i = 0; $i += ++$i; echo $i; // Outputs 2. However, in Javascript: var i = 0; i += ++i; console.log(i); // Outputs 1. So it looks like that in Javascript, it makes copy of i and doesn't reference the variable. Is this intentional and if yes, why? From EcmaScript

Possible Duplicate: Undefined Behavior and Sequence Points Pleae explain the behaviour of following statements int b=3; cout<<b++*++b<<endl; How will it be calculated? Greg Howell The behavior here is undefined. See this question Relevant standard quote: §5/4.1 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. The most common sequence point is the end of a statement. Also worth noting from the standard: §5.2.2/8 The order of evaluation of arguments is unspecified. The standard says this is

Possible Duplicate: Could anyone explain these undefined behaviors (i = i++ + ++i , i = i++, etc…) What is the difference between i = ++i; and ++i; where i is an integer with value 10 ? According to me both do the same job of incrementing i i.e after completion of both the expressions i =11 . i = ++i; invokes Undefined Behaviour whereas ++i; does not. C++03 [Section 5/4] says 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 . In i = ++i i is being modified twice[pre-increment and assignment]

I have a question about these two C statements: x = y++; t = *ptr++; With statement 1, the initial value of y is copied into x then y is incremented. With statement 2, We look into the value pointed at by *ptr, putting that into variable t, then sometime later increment ptr. For statement 1, the suffix increment operator has higher precedence than the assignment operator. So shouldn't y be incremented first and then x is assigned to the incremented value of y? I'm not understanding operator precedence in these situations. You're mistaken about the meaning of your 2] . Post-increment always

The array.prototype.reduce function at: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce It has the following loop: for (index = 0; length > index; ++index) { if (this.hasOwnProperty(index)) { if (isValueSet) { value = callback(value, this[index], index, this); } else { value = this[index]; isValueSet = true; } } } I don't think there is a difference whether the index is pre or post incremented here since it's done after the loop iterates each time, but want to be certain. Can this be changed to index += 1 so it passes jslint? Please don't debate

I am trying to understand how pointer incrementing and dereferencing go together, and I did this to try it out: #include <stdio.h> int main(int argc, char *argv[]) { char *words[] = {"word1","word2"}; printf("%p\n",words); printf("%s\n",*words++); printf("%p\n",words); return 0; } I expected this code to do one of these: First dereference then increase the pointer (printing word1) First dereference then increase the value (printing ord1) Dereference pointer + 1 (printing word2) But compiler won't even compile this, and gives this error: lvalue required as increment operand am I doing something