Lazy Evaluation not so Lazy?
c#, lazy-evaluation
Solution
I've always heard C# uses lazy evaluation.
That's far too vague a comment for me to agree with. If you'd said that the `||` and `&&` operators in C# are short-circuiting, only evaluating the second operand if the overall result couldn't be determined just from the first operand, then I'd agree with it. Lazy evaluation is a more wide-ranging concept - for example, LINQ queries use lazy (or deferred) evaluation, not actually fetching any data until the result is used.
You're using the `&` operator, which isn't short-circuiting:
The & operator evaluates both operators regardless of the first one's value.
The `&&` operator is short-circuiting:
The operation `x && y` corresponds to the operation `x & y` except that if `x` is false, `y` is not evaluated, because the result of the AND operation is false no matter what the value of `y` is.
Replace `&` with `&&` everywhere in your code, and you'll see "argument is true!" printed 8 times (not 7 - count your comments again).
Problem
I've always heard C# uses lazy evaluation. So for certain code like, `if (true || DoExpensiveOperation()` will return `true` without executing `DoExpensiveOperation()`. On an interview test I saw the following questions, ``` static bool WriteIfTrue(bool argument) { if (argument) { Console.WriteLine("argument is true!"); } return argument; } static void Main() { // 1 0 0 1 WriteIfTrue((WriteIfTrue(false) & WriteIfTrue(true)) || WriteIfTrue(true)); // 1 1 0 1 WriteIfTrue((WriteIfTrue(true) || WriteIfTrue(false)) & WriteIfTrue(true)); // 0 0 0 0 WriteIfTrue((WriteIfTrue(false) & WriteIfTrue(true)) & WriteIfTrue(false)); // 1 1 0 1 WriteIfTrue((WriteIfTrue(true) || WriteIfTrue(false)) & WriteIfTrue(true)); } ``` How many times would it print "argument is true!" to the screen? I would say `7` is the correct answer. Now if I stick into the compiler and run it, it prints it `10` times! Where did lazy evaluation all go wrong?