Quoting from the reference documentation: Python evaluates expressions from left to right. So yes, you can count on that (with one exception, see below). A call (the (…) part after a primary, such as a function name) is just another expression primary, and the arguments for the call are just more expressions. Note: There is … Read more
All the answers explaining why you get 2 and not 1 are actually wrong. According to the PHP documentation, mixing + and ++ in this manner is undefined behavior, so you could get either 1 or 2. Switching to a different version of PHP may change the result you get, and it would be just … Read more
The first one is equivalent to: (true ? (++x, ++y) : (–x)), –y; The second one is equivalent to: (false ? (++x, ++y) : (–x)), –y; Thus the –y is always executed. In the first line, the increments are executed first so x = 1, y = 0 is expected. In the second line, the … Read more
Note: The two defect reports DR#637 and DR#222 are important to understand the below’s behavior rationale. For explanation, in C++0x there are value computations and side effects. A side effect for example is an assigment, and a value computation is determining what an lvalue refers to or reading the value out of an lvalue. Note … Read more
Explanation Prec. denotes operator precedence, where group 1 has the highest precedence and group 17 the lowest. Assoc. denotes operator associativity, where such is applicable. Associativity can be either left-to-right or right-to-left. Sources My ambition with this post is to provide a operator precedence table on-site at Stack Overflow, which is correct and canonical. This … Read more
Yes, it’s guaranteed, otherwise such operators would lose much of their usefulness. Important notice: this is valid only for the builtin && and ||; if some criminal overloads them, they are treated as “regular” overloaded binary operators, so in this case both operands are always evaluated, and in unspecified order as usual. For this reason, … Read more
Yes, left to right evaluation order is guaranteed, with the exception of assignments. That’s documented here (py2, py3): Python evaluates expressions from left to right. Notice that while evaluating an assignment, the right-hand side is evaluated before the left-hand side. In the following lines, expressions will be evaluated in the arithmetic order of their suffixes: … Read more
According to ISO/IEC 14882:2003(E) section 12.6.2: Initialization shall proceed in the following order: First, and only for the constructor of the most derived class as described below, virtual base classes shall be initialized in the order they appear on a depth-first left-to-right traversal of the directed acyclic graph of base classes, where “left-to-right” is the … Read more
You need to bracket the ternary conditionals: <?php for ($a=0; $a < 7; $a++) { echo ( $a == 1 ? ‘one’ : ($a == 2 ? ‘two’ : ($a == 3 ? ‘three’ : ($a == 5 ? ‘four’ : ‘other’)))); echo “\n”; // prints ‘four’ } exit; ?> returns: other one two three … Read more
The short answer is that right-associativity can improve readability by making what the programmer type consistent with what the program actually does. So, if you type ‘1 :: 2 :: 3‘, you get a List(1, 2, 3) back, instead of getting a List back in a completely different order. That would be because ‘1 :: … Read more