The code exhibits unspecified behavior due to unspecified order of evaluation of sub-expressions although it does not invoke undefined behavior since all side effects are done within functions which introduces a sequencing relationship between the side effects in this case. This example is mentioned in the proposal N4228: Refining Expression Evaluation Order for Idiomatic C++ … Read more
Grouping (this is what non-comparison operators do): a + b + c means (a + b) + c Chaining (this is what comparison operators do): a < b < c means (a < b) and (b < c) Grouping left to right (this is the way things are grouped): 5 – 2 – 1 means … Read more
It’s NOT, AND, OR, from highest to lowest according to the documentation on Operator precedence Here is the complete precedence table, lowest precedence to highest. A row has the same precedence and chains from left to right 0. := 1. lambda 2. if – else 3. or 4. and 5. not x 6. in, not … Read more
Use: h.className = h.className + (h.className ? ‘ error’ : ‘error’) You want the operator to work for h.className. Better be specific about it. Of course, no harm should come from h.className += ‘ error’, but that’s another matter. Also, note that + has precedence over the ternary operator: JavaScript Operator Precedence
In C the ternary operator is defined like logical-OR-expression ? expression : conditional-expression where conditional expression is defined like logical-OR-expression The assignment operator has a lower priority than the OR operator. Thus you have to write a >= 5 ? b = 100 : ( b = 200 ); Otherwise the compiler consideres the expression … Read more
You ask two questions: 1. Why can’t I refer to the SELECT cost alias at the WHERE clause? 2. But why order by cost desc; is allowed? The manual has an answer for both of them here: An output column’s name can be used to refer to the column’s value in ORDER BY and GROUP … Read more
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
The operator precedence in the C/C++ language in not defined by a table or numbers, but by a grammar. Here is the grammar for conditional operator from C++0x draft chapter 5.16 Conditional operator [expr.cond]: conditional-expression: logical-or-expression logical-or-expression ? expression : assignment-expression The precedence table like this one is therefore correct when you use assignment on … 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
There is a difference between an expression being evaluated and completing its side effects. The b = a assignment expression will be evaluated ahead of subtraction due to higher precedence of the parentheses. It will provide the value of a as the result of the evaluation. The writing of that value into b, however, may … Read more