My rule of thumb, which covers basically 99% of all use cases for conditional statements, is: Grouping: () Member access . or […] Not: ! Comparison, e.g. < , >= , === , !=, … Logical AND && Logical OR || MDN gives you the exhaustive breakdown: JavaScript Operator Precedence So for your example: (firstRun … Read more
This is one of those little gotcha’s that make C and C++ so much fun. If you want to bend your brain, figure out this one: while (*dst++ = *src++) ; It’s a string copy. The pointers keep getting incremented until a character with a value of zero is copied. Once you know why this … Read more
TL;DR Python reads the expression as [0xf or (x in (1, 2, 3))], because: The Python tokenizer. Operator precedence. It never raises NameError thanks to short-circuit evaluation – if the expression left to the or operator is a truthy value, Python will never try to evaluate the right side of it. Parsing hexadecimal numbers First, … Read more
The Java Tutorials has a list illustrating operator precedence. The equality operators will be evaluated first, then &&, then ||. Parentheses will be evaluated before anything else, so adding them can change the order. This is usually pretty much the same from language to language, but it’s always a good idea to double check. It’s … Read more
From the Java Language Specification (on Expressions): 15.7.4 Argument Lists are Evaluated Left-to-Right In a method or constructor invocation or class instance creation expression, argument expressions may appear within the parentheses, separated by commas. Each argument expression appears to be fully evaluated before any part of any argument expression to its right.
Change the first false by true. I know it seems stupid to have (true || true) but it proves your point. bool result = true || true && false; // –> true result = (true || true) && false; // –> false result = true || (true && false); // –> true
According to the Operator Precedence, comma operator has lower precedence than operator=, so x = 2,3; is equivalent to (x = 2),3;. (Operator precedence determines how operator will be bound to its arguments, tighter or looser than other operators according to their precedences.) Note the comma expression is (x = 2),3 here, not 2,3. x … Read more
Let me say this very clearly, because people misunderstand this all the time: Order of evaluation of subexpressions is independent of both associativity and precedence. Associativity and precedence determine in what order the operators are executed but do not determine in what order the subexpressions are evaluated. Your question is about the order in which … Read more
You are actually doing this: var_dump(0b10 & (0b01 == 0)); var_dump(0b10 & (0b01 != 0)); Try: var_dump((0b10 & 0b01) == 0); var_dump((0b10 & 0b01) != 0);
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