increment

I have been fooling around with some code and saw something that I don't understand the "why" of. int i = 6; int j; int *ptr = &i; int *ptr1 = &j j = i++; //now j == 6 and i == 7. Straightforward. What if you put the operator on the left side of the equals sign? ++ptr = ptr1; is equivalent to (ptr = ptr + 1) = ptr1; whereas ptr++ = ptr1; is equivalent to ptr = ptr + 1 = ptr1; The postfix runs a compilation error and I get it. You've got a constant "ptr + 1" on the left side of an assignment operator. Fair enough. The prefix one compiles and WORKS in C++. Yes, I understand it's messy and you're

This question already has an answer here: How do I create a variable number of variables? 14 answers In Python, if I were to have a user input the number X, and then the program enters a for loop in which the user inputs X values, is there a way/is it a bad idea to have variable names automatically increment? ie: user inputs '6' value_1 = ... value_2 = ... value_3 = ... value_4 = ... value_5 = ... value_6 = ... Can I make variable names increment like that so that I can have the number of variables that the user inputs? Or should I be using a completely different method such as appending all

In x = x + 1 , is x evaluated twice? If so, does that mean in x += 1 , x is only evaluated once? How are the two expressions evaluated in terms of compiler intermediate code? For example, x++ could mean : take the location of x , load the contents of x into a register, and increment the value of x in memory. Also I have read that x += 1 is useful when x is not a simple variable, but an expression involving an array. Any ideas why this is the case? In most compilers these would be identical Just to give you a "real-world" example, consider this program: int main() { int i = 0; i += 1; i++; i =

What is the difference between += and =+? Specifically, in java, but in general also. i += 4; means i = i + 4; // increase i by 4. While i =+ 4; is equivalent to i = +4; // assign 4 to i. the unary plus is effectively no-op. (See http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.15.3 for what a unary + does.) += is an operator that increments the left-hand side of the assignment by the value of the right-hand side and assigns it back to the variable on the left-hand side. =+ is not an operator but, in fact, two operators: the assignment operator = and the unary plus +

I have just started to learn C, and I get that *a = *b; a++; b++; and *a++ = *b++ are equivalent, but is that what's actually happening when the line *a++ = *b++ is called? Can someone clarify how the compiler is interpreting the second line? I know about right-to-left precedence and such, but can someone precisely write the steps the compiler uses to interpret this line of code? You said that you believe that: *a = *b; a++; b++; is equivalent to *a++ = *b++; but that is false, so you have a false belief. Let's correct your false belief. In the first case, the following things must happen: VAR

Possible Duplicates: Why does this go into an infinite loop? Things like i = i++ have undefined behavior in C and C++ because the value of a scalar object is changes twice within the same expression without intervening sequence point. However I suppose that these kind of expressions have well-defined behavior in C# or Java because AFAIK the evaluation of argument goes left to right and there are sequence points all over. That said, I'd expect i = i++ to be equivalent to i++ . But it's not. The following program outputs 0 . using System; class Program { static void Main(string[] args) { int i =

How are they different? Here's what I'm thinking, but I'm not sure.... If you use pre-incrementation, for example in a for loop with ++j, then you are basically saying: "Make a copy of the value of j for use in the loop, then increment j, then go through the statements in the loop with the copy of j." If you are using post-incrementation in the same loop j++, then you are basically saying: "Make a copy of the value of j for use in the loop, then go through the statements in the loop with the copy of j, then increment j." The reason I'm unsure is because I've created a for loop that multiplies